As filed with the Securities and Exchange Commission
                               on August 12, 1997

                                                       Registration No. 333-1535
       -----------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                         POST EFFECTIVE AMENDMENT NO. 1
                                       TO
                                    FORM S-3
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                   ENZON, INC.
             (Exact name of registrant as specified in its charter)

     DELAWARE                                                       22-2372868
 (State or other juris-                                        (I.R.S. Employer
 diction of incorporation                                    Identification No.)
    or organization)

               20 Kingsbridge Road, Piscataway, New Jersey 08854
                                 (732) 980-4500
               (Address, including zip code, and telephone number,
                 including area code, of registrant's principal
                               executive offices)

                                JOHN CARUSO, ESQ.
                      VICE PRESIDENT, BUSINESS DEVELOPMENT,
                          GENERAL COUNSEL AND SECRETARY
                                   ENZON, INC.
                20 Kingsbridge Road, Piscataway, New Jersey 08854
                                 (732) 980-4500

            (Name, address, including zip code, and telephone number,
                   including area code, of agent for service)

                                   Copies to:

                             KEVIN T. COLLINS, ESQ.
                                 ROSS & HARDIES
                  65 East 55th Street, New York, New York 10022
                                 (212) 421-5555


         Approximate  date of  commencement  of proposed sale to the public:  As
soon as practicable after this Registration Statement becomes effective.








         If the only securities  being registered on this Form are being offered
pursuant to dividend or interest  reinvestment plans, please check the following
box. [ ]

     If any  securities  being  registered  on this Form are to be  offered on a
delayed or continuous  basis  pursuant to Rule 415 under the  Securities  Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box. [X]

         If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list  the  Securities  Act  registration  statement  number  of the  earlier
effective registration statement for the same offering. [ ]

         If this  Form is a  post-effective  amendment  filed  pursuant  to Rule
462(b) under the Securities Act, check the following box and list the securities
registration  statement number of the earlier effective  registration  statement
for the same offering. [ ]

     If delivery of the  prospectus is expected to be made pursuant to Rule 434,
please check the following box. [ ]




                 SUBJECT TO COMPLETION --- DATED AUGUST 12, 1997

         Information  contained herein is subject to completion or amendment.  A
registration  statement  relating  to these  securities  has been filed with the
Securities and Exchange Commission (the "Commission").  These securities may not
be sold nor may  offers to buy be  accepted  prior to the time the  registration
statement  becomes  effective.  This prospectus shall not constitute an offer to
sell or the solicitation of an offer to buy nor shall there be any sale of these
securities  in any State in which  such  offer,  solicitation  or sale  would be
unlawful prior to registration or qualification under the securities laws of any
such State.


                                   PROSPECTUS

                                   ENZON, INC.
- -----------------------------------------------------------------------------

                                2,070,466 Shares
                                  Common Stock
                                ($.01 par value)


         This prospectus (the "Prospectus")  relates to the offer and sale of up
to 2,070,466  shares of common stock,  $.01 par value (the "Common  Stock"),  of
Enzon Inc.  (the  "Company"  or "Enzon") by certain  selling  stockholders  (the
"Selling  Stockholders").  Of such 2,070,466  shares of Common Stock (i) 595,157
shares (the "Outstanding Common Shares") are outstanding and held by the Selling
Stockholders;  (ii) 638,686  shares (the  "Warrant  Shares")  are issuable  upon
exercise  of  outstanding   warrants  (the   "Warrants")  held  by  the  Selling
Stockholders  and (iii) up to  836,623  shares  (the  "Additional  Shares")  are
additional  shares which may be issued to the Selling  Stockholders  pursuant to
the Registration Rights Agreement (the "Registration  Rights Agreement") entered
into by the Company and the Selling  Stockholders in connection with the Private
Placement (as hereinafter  defined),  upon the occurrence of certain events,  as
hereinafter described (each a "Triggering Event").

         In a private  placement  transaction  which closed in January 1996 (the
"Private  Placement"),  one of the  Selling  Stockholders,  Clearwater  Fund  IV
Limited  ("Limited"),  purchased  1,094,890  shares of Common Stock,  and 40,000
shares of the  Company's  Series B  Convertible  Preferred  Stock (the "Series B
Preferred  Shares"),  and was issued a warrant for no separate  consideration to
purchase  638,686  shares  of  Common  Stock.  Limited  converted  the  Series B
Preferred  Shares into  2,030,456  shares of Common Stock.  All of the shares of
Common Stock issued upon conversion of the Series B Preferred Shares and 497,733
of the shares of Common Stock purchased by Limited in the Private Placement have
previously  been  sold.  Pursuant  to the terms of a Warrant  Purchase  and Sale
Agreement dated as of March 10, 1997 (the "Warrant Purchase Agreement"), Limited
sold  warrants to purchase  364,963  shares of Common Stock to the other Selling
Stockholder,  Clearwater Fund IV LLC ("LLC").  The Outstanding Common Shares and
the shares of Common  Stock to be received  upon  exercise of the  Warrants  are
being offered by the Selling  Stockholders  hereby. The Warrants are exercisable
at a per share  exercise  price of $4.11 (as may be adjusted in accordance  with
the terms of the  Warrants)  and expire on  February  7, 2001.  The  Outstanding
Common Shares,  the Warrant Shares and the  Additional  Shares are  collectively
referred to herein as the "Common Shares."

         Pursuant to the terms of the Registration Rights Agreement, the Company
may be required to issue an indeterminate  number of additional shares of Common
Stock  upon the  occurrence  of a  Registration  Rights  Triggering  Event.  The
Registration  Rights  Triggering  Events  are  substantially  identical  to  the
Certificate of Designations Triggering Events. Up to a maximum of 836,623 of the
Shares of Common Stock to be received upon the occurrence of a Triggering  Event
are being offered by the Selling  Stockholders  hereby. In the event the Company
is  required to issue in excess of 836,623  shares of its Common  Stock upon the
occurrence  of a  Triggering  Event,  the  Company  may be  required  to file an
additional  registration  statement to cover such additional  shares.  See "Risk
Factors - Possible Volatility of Stock Price" and "Selling Stockholders."



         The Selling  Stockholders  may sell the Common Shares from time to time
in  transactions  in  the  open  market,  in  negotiated  transactions,  or by a
combination  of these  methods,  at fixed prices that may be changed,  at market
prices at the time of sale, at prices  related to market prices or at negotiated
prices.  The Selling  Stockholders may effect these  transactions by selling the
Common Shares to or through broker-dealers,  who may receive compensation in the
form of  discounts  or  commissions  from the Selling  Stockholders  or from the
purchasers of the Common Shares for whom the  broker-dealers may act as agent or
to whom they may sell as principal, or both.
See "Plan of Distribution."

         The Company will bear all expenses in connection with the  registration
of the Common Shares  herein,  which  expenses are estimated to be $30,500.  The
Selling Stockholders will pay any brokerage  compensation in connection with its
sale of the Common Shares. The Company will not receive any of the proceeds from
the sale of the  Common  Shares  by the  Selling  Stockholder,  but may  receive
proceeds  of up to  $2,625,000  upon  exercise  of the  Warrants.  See  "Use  of
Proceeds."

         The Company's Common Stock is traded in the over-the-counter market and
is quoted on the Nasdaq National  Market,  under the symbol "ENZN." On August 6,
1997 the reported last sale price of the Common Stock, as reported on the Nasdaq
National Market was $3.8125 per share.


AN INVESTMENT IN THE SECURITIES OFFERED HEREBY INVOLVES A HIGH DEGREE OF RISK.
SEE "RISK FACTORS" COMMENCING ON PAGE 5.

THESE  SECURITIES  HAVE NOT BEEN APPROVED OR  DISAPPROVED  BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES  COMMISSION,  NOR HAS THE SECURITIES
AND  EXCHANGE  COMMISSION  OR ANY STATE  SECURITIES  COMMISSION  PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

                 The date of this Prospectus is August __, 1997



                                TABLE OF CONTENTS


                                                              Page


Available Information....................................        1

Incorporation of Certain Documents by Reference..........        1

Prospectus Summary.......................................        2

Risk Factors.............................................        5

Use of Proceeds..........................................        9

Selling Stockholders......................................       9

Plan of Distribution.....................................       10

Legal Matters............................................       11

Experts..................................................       11



No one has been authorized to give any information or to make any representation
not contained or incorporated by reference in this Prospectus in connection with
this offering.  Any information or representation  not contained or incorporated
by  reference  herein  must not be relied on as having  been  authorized  by the
Company.   This  Prospectus  does  not  constitute  an  offer  to  sell  or  the
solicitation  of an offer to buy the  securities  offered hereby in any state to
any person to whom it is  unlawful  to make such offer or  solicitation.  Except
where otherwise indicated, this Prospectus speaks as of its date and neither the
delivery  of this  Prospectus  nor any sale  made  hereunder  shall,  under  any
circumstances,  create  an  implication  that  there  has been no  change in the
affairs of the Company since the date hereof.





                              AVAILABLE INFORMATION

         The  Company  is  subject  to  the  informational  requirements  of the
Securities  Exchange  Act of 1934,  as  amended  (the  "Exchange  Act"),  and in
accordance therewith files reports,  proxy statements and other information with
the Securities and Exchange Commission. Such reports, proxy statements and other
information  filed by the  Company  can be  inspected  and  copied at the public
reference  facilities  maintained by the  Commission at 450 Fifth Street,  N.W.,
Washington, D.C. 20549, and at the following Regional Offices of the Commission:
New York Regional  Office,  Seven World Trade Center,  Suite 1300, New York, New
York 10048; and Chicago Regional Office,  Northwestern  Atrium Center,  500 West
Madison  Street,  Suite  1400,  Chicago,  Illinois  60661-2511.  Copies  of such
material can be obtained from the Public Reference  Section of the Commission at
450 Fifth Street, N.W., Washington, D.C. 20549 at prescribed rates.

         The Company's  Securities are listed on the Nasdaq  National Market and
reports and other  information  concerning  the Company can be  inspected at the
National  Association  of Securities  Dealers,  1735 K Street,  N.W., 4th Floor,
Washington, D.C.
20006-1506.

         The Company has filed with the Commission a  Registration  Statement on
Form S-3 (the  "Registration  Statement") under the Securities Act, with respect
to the shares of Common Stock offered  hereby.  This Prospectus does not contain
all of the information set forth in the Registration  Statement and the exhibits
and schedules thereto.  For further  information with respect to the Company and
the shares of Common  Stock  offered  hereby,  reference  is hereby  made to the
Registration Statement, exhibits and schedules.

         The following  trademarks and service marks appear in this  Prospectus:
ADAGEN(R) and ONCASPAR(R) are registered trademarks of the Company; PEGNOLOGY(R)
is a registered service mark of the Company; SCA(R) is a registered trademark of
Enzon Labs Inc., a  wholly-owned  subsidiary  of the  Company;  Intron A(R) is a
registered trademark of Schering Corporation.


                 INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

         The Company hereby  incorporates  by reference into this Prospectus (i)
its Annual  Report on Form 10-K for the Fiscal Year Ended June 30,  1996,  which
contains audited  financial  statements for the Company's latest fiscal year for
which a Form 10-K was required to have been filed and  incorporates by reference
certain  portions of the  Company's  definitive  Proxy  Statement for the Annual
Meeting of  Stockholders  held  December 3, 1996 (ii) all other reports filed by
the Company  pursuant to Section  13(a) or 15(d) of the  Exchange Act since June
30, 1996,  including but not limited to, the  Quarterly  Report on Form 10-Q for
the Quarter Ended September 30, 1996, the Quarterly  Report on Form 10-Q for the
Quarter  Ended  December 31,  1996,  the  Quarterly  Report on Form 10-Q for the
Quarter Ended March 31, 1997,  and the Current  Reports on Form 8-K filed by the
Company with the Commission on each of July 22, 1996, November 4, 1996, December
20, 1996, January 16, 1997,  January 27, 1997,  February 28, 1997, and March 10,
1997, and (iii) the description of the Company's  Common Stock,  $.01 par value,
as  contained  in its  registration  statement  on  Form  8-A,  filed  with  the
Commission on October 29, 1984, as amended by a Form 8 filed with the Commission
on October 15, 1990.

         All documents filed by the Company  pursuant to Sections 13(a),  13(c),
14 and 15(d) of the Exchange Act, subsequent to the date hereof and prior to the
filing  of a  post-effective  amendment  to  the  Registration  Statement  which
indicates that all shares of Common Stock offered hereby have been sold or which
deregisters all shares of Common Stock then remaining unsold, shall be deemed to
be  incorporated  by reference into this Prospectus and to be a part hereof from
the date of filing of such documents.

         Any statement contained herein or in a document  incorporated or deemed
to be  incorporated  by  reference  herein  shall be  deemed to be  modified  or
superseded for purposes of this  Prospectus to the extent that such statement is
modified or  superseded  by a statement  contained  herein or in a  subsequently
filed  document  which  also is or is deemed  to be  incorporated  by  reference
herein. Any such statement so modified or superseded shall not be deemed, except
as so modified or superseded, to constitute a part of this Prospectus.

         The Company will provide, without charge, to each person (including any
beneficial  owner) to whom this  Prospectus is  delivered,  upon written or oral
request of such person,  a copy of any and all of the information  that has been
incorporated  by reference in this  Prospectus  (not including  exhibits to such
information unless such exhibits are specifically incorporated by reference into
such  information).  Such  requests  should be  directed  to John  Caruso,  Vice
President, Business Development, General Counsel and Secretary, at the Company's
principal  executive  offices at 20  Kingsbridge  Road,  Piscataway,  New Jersey
08854, telephone (732) 980-4500.



                               PROSPECTUS SUMMARY

The  following  summary is  qualified  in its  entirety by reference to the more
detailed  information and consolidated  financial statements appearing elsewhere
and incorporated by reference in this Prospectus.


                                   The Company

         The Company is a biopharmaceutical company that develops,  manufactures
and markets  enhanced  therapeutics  for  life-threatening  diseases through the
application of its proprietary technologies, PEG Modification or the PEG Process
and Single-Chain Antigen-Binding (SCA(R)) proteins.

         The Company has received marketing approval from the United States Food
and  Drug  Administration  ("FDA")  for two of its  products:  (i)  ONCASPAR(R),
approved in February  1994 for the  indication of acute  lymphoblastic  leukemia
("ALL") in patients who are hypersensitive to native forms of L-asparaginase and
(ii) ADAGEN(R),  the first successful  application of enzyme replacement therapy
for an inherited disease, approved in March 1990, to treat a rare form of Severe
Combined  Immunodeficiency  Disease ("SCID"),  commonly known as the "Bubble Boy
Disease".

         The  Company  manufactures  both  ADAGEN  and  ONCASPAR  in  its  South
Plainfield,  New  Jersey  facility  and  markets  ADAGEN on a  worldwide  basis.
ONCASPAR is marketed in the U.S. by Rhone-Poulenc  Rorer  Pharmaceuticals,  Inc.
("RPR") and in Europe by Medac Gmbh ("Medac").  The Company received  $6,000,000
from RPR  related to the  granting of the U.S.  license and is also  entitled to
royalties  on the sales of ONCASPAR in the U.S. by RPR of 23.5% to 43.5%,  based
on the sales  level of  ONCASPAR.  Royalties  payable to the  Company by RPR are
being offset against an original credit of $5,970,000, which includes $3,500,000
in advance  royalties  received by the Company in fiscal 1995.  In October 1996,
the Company entered into a marketing agreement with Medac for ONCASPAR in Europe
and Russia.  Medac will  purchase  ONCASPAR from Enzon at a set price which will
increase over the term of the  agreement.  The agreement  also contains  certain
minimum annual  purchase  requirements.  The Company has also granted  exclusive
licenses to sell  ONCASPAR  in Canada and Mexico to RPR in exchange  for royalty
payments on future  sales and is  currently  pursuing  additional  licenses  for
marketing and distribution rights outside North America,  Europe and Russia. RPR
and Medac are currently  conducting clinical trials in expanded  indications for
ONCASPAR.

         ONCASPAR is the enzyme  L-asparaginase  modified by the  Company's  PEG
Process and ADAGEN is the enzyme adenosine  deaminase  modified by the Company's
PEG Process. The PEG Process involves chemically  attaching  polyethylene glycol
("PEG"), a relatively non-reactive and non-toxic polymer, to proteins, chemicals
and certain other pharmaceuticals for the purpose of enhancing their therapeutic
value. The attachment of PEG helps to disguise the modified  compound and reduce
the recognition of the compound by the immune system, thereby generally lowering
potential   immunogenicity.   Both  the  increased   molecular  size  and  lower
immunogenicity  result in extended  circulating  blood life,  in some cases from
minutes to days. The PEG Process also significantly  increases the solubility of
the modified  compound which enhances the delivery of the native  compound.  The
PEG Process was  originally  covered by a broad patent which expired in December
1996. The Company has made significant  improvements to the original PEG Process
and has applied for and received several patents for such improvements.

         The Company recently has developed  technology that gives  PEG-modified
compounds "Pro Drug" attributes.  This is accomplished by attaching PEG by means
of a covalent bond that is designed to deteriorate over time,  thereby releasing
the therapeutic  moiety  (therapeutic  part of the compound) in the proximity of
the target tissue. These attributes could significantly  enhance the therapeutic
value of new chemicals,  as well as drugs already marketed. The Company believes
that this "Pro  Drug/Transport  Technology" has broad usefulness and that it can
be  applied  to a wide  range of  drugs,  such as  cancer  chemotherapy  agents,
antibiotics,  anti-fungals  and  immunosuppressants,  as well as to proteins and
peptides, including enzymes and growth factors. The markets for

                                      - 2 -



these  drugs and  biologicals  have large  potential  patient  populations.  The
Company is  currently  applying  its Pro  Drug/Transport  Technology  to certain
anticancer agents that are in the early research stage.

         The  Company's  lead  development  candidate,   PEG-hemoglobin,   is  a
hemoglobin-based  oxygen  carrier,  commonly  referred  to as a red  blood  cell
substitute, and is currently being developed by the Company as a radiosensitizer
for use with radiation  treatment of solid hypoxic tumors.  Preclinical  studies
conducted at Enzon,  the University of Wisconsin  School of Veterinary  Medicine
and Dana Farber Cancer Institute, indicate that PEG- hemoglobin may be useful in
treating solid tumors. These studies suggest that PEG-hemoglobin delivers oxygen
to solid hypoxic tumors,  thereby  enhancing the ability of radiation therapy to
significantly decrease the size of these tumors.

         During  fiscal 1996,  the Company  completed a Phase I safety study for
PEG-hemoglobin  in  which  34  normal  volunteers  received  a  single  dose  of
PEG-hemoglobin  in amounts up to 45 grams,  the equivalent of 1.5 units of whole
blood. The Company is currently conducting a multi-dose,  multi-center  clinical
trial of  PEG-hemoglobin  in  cancer  patients  receiving  radiation  treatment.
Patients  entering  this  new  trial  receive  once-a-week   infusions  of  PEG-
hemoglobin followed by five days of radiation  treatment.  The protocol for this
study calls for this to be repeated weekly for three weeks.  The primary purpose
of this trial is to evaluate safety related to multiple doses of PEG- hemoglobin
and radiation therapy. It is estimated that approximately 800,000 cases of solid
hypoxic tumors are diagnosed each year in the United States.

         The  Company  is  pursuing  a dual  strategy  for  commercializing  its
proprietary technologies.  In addition to developing and manufacturing products,
using the Company's  proprietary  technology,  and marketing such products,  the
Company  has  established  strategic  alliances  in  which  Enzon  licenses  its
proprietary  technologies  and  products in  exchange  for  milestone  payments,
manufacturing revenues and/or royalties.

         One such license is the Company's  agreement with Schering  Corporation
("Schering")  to apply  the PEG  Process  to  Schering's  product,  INTRON  A(R)
(interferon  alfa  2b),  a  genetically-engineered   anticancer-antiviral  drug.
Schering has reported that the PEG-modified  version of INTRON A is currently in
clinical  trials.  Under the agreement,  the Company is entitled to royalties on
worldwide  sales  of  PEG-INTRON  A,  if  any,  and  payments  of  approximately
$5,500,000  subject to the  achievement  of certain  milestones in the product's
development.  Sales by  Schering  of the  unmodified  version  of  INTRON A were
reported  as $524  million  for  1996.  The  Company  has the  option,  upon FDA
approval,  to be Schering's exclusive  manufacturer of PEG-INTRON A for the U.S.
market.

         The Company also has an extensive licensing program for its SCA protein
technology.  SCA  proteins  are  genetically  engineered  proteins  designed  to
overcome  the  problems   hampering  the  diagnostic  and   therapeutic  use  of
conventional  monoclonal  antibodies.  Pre-clinical  studies have shown that SCA
proteins target and penetrate tumors more readily than  conventional  monoclonal
antibodies. In addition to these advantages,  because SCA proteins are developed
at the gene level,  they are better suited for targeted delivery of gene therapy
vectors and fully-human SCA proteins can be isolated directly,  with no need for
costly "humanization"  procedures.  Also, many gene therapy methods require that
proteins be produced in active form inside  cells.  SCA proteins can be produced
through  intracellular  expression  (inside cells) more readily than  monoclonal
antibodies.

         Currently,  there are nine SCA proteins in Phase I or Phase II clinical
trials by various  institutions,  including a product  developed by the Company,
SCA-CC49.  Some of the areas being explored are cancer  therapy,  cardiovascular
indications and AIDS.

         The Company has granted non-exclusive SCA licenses to more than a dozen
companies,  including  Bristol-  Myers Squibb,  Inc.  ("Bristol-Myers"),  Baxter
Healthcare Corporation ("Baxter"), Eli Lilly & Co. ("Eli Lilly") and the Gencell
division of RPR  ("RPR/Gencell").  These licenses  generally provide for upfront
payments, milestone payments and royalties on sales of FDA approved products.


                                      - 3 -


                                  The Offering

Securities Offered.......

     This Prospectus relates to an offering by the Selling Stockholders of up to
2,070,466  shares of Common  Stock of the  Company.  Of these shares (i) 595,157
shares are  Outstanding  Common  Shares  issued in the Private  Placement;  (ii)
638,686  shares are  Warrant  Shares  which may be issued  upon  exercise of the
Warrants  held  by  the  Selling  Stockholders  and  (iii)  836,623  shares  are
Additional  Shares  which  may be issued to the  Selling  Stockholders  upon the
occurrence  of a Triggering  Event.  The actual number of shares of Common Stock
issued to the Selling  Stockholders  and sold hereby will depend upon  whether a
Triggering  Event occurs and the duration of such Triggering  Event. The Company
believes  that the  number of shares of Common  Stock to which  this  Prospectus
relates  should be the maximum  number of shares of Common Stock that are likely
to be issued to the Selling  Stockholders and sold hereby,  and expects that the
actual number of shares of Common Stock issued to the Selling  Stockholders  and
sold  hereby  will be less  than such  number.  See  "Risk  Factors  -  Possible
Volatility of Stock Price" and "Selling Stockholders."

Securities Outstanding...

     As of August 1, 1997,  the Company had  30,805,515  shares of Common  Stock
outstanding.  Assuming that the Warrants are exercised for the maximum number of
shares of Common  Stock and no  Triggering  Event  occurs and no other shares of
Common Stock are issued  subsequent  to August 1, 1997,  the Company  would have
31,436,421 shares of Common Stock outstanding. See "Selling Stockholders."

Use of Proceeds.........

     The  Company  will not  receive  any  proceeds  from the sale of the Common
Shares offered herein by the Selling  Stockholders.  To date the Company has not
received any proceeds  from the  exercise of the  Warrants.  If the Warrants are
exercised in their entirety the Company will receive estimated gross proceeds of
approximately  $2,625,000.  The Company intends to utilize any proceeds received
from the exercise of the Warrants for general corporate  purposes.  There can be
no assurance that the Warrants will be exercised. See "Use of Proceeds."

Risk Factors.......... 

     See "Risk  Factors" for a discussion of certain risk factors that should be
considered  by  prospective  investors in  connection  with an investment in the
shares of Common Stock offered hereby.


                                      - 4 -


                                  RISK FACTORS

         Information  contained and incorporated by reference in this Prospectus
contains  "forward-looking  statements"  which can be  identified  by the use of
forward-looking  terminology  such  as  "believes,"  "expects,"  "may,"  "will,"
"should," or "anticipates"  or the negative thereof or other variations  thereon
or comparable  terminology,  or by discussions of strategy.  No assurance can be
given that the future results covered by the forward-looking  statements will be
achieved.  The risk  factors set forth below  constitute  cautionary  statements
identifying  important factors with respect to such forward-looking  statements,
including  certain risks and  uncertainties,  that could cause actual results to
vary  materially  from the future  results  indicated in such  forward-  looking
statements.  Other  factors could also cause actual  results to vary  materially
from the future results indicated in such forward-looking statements.

         An  investment  in the Common  Shares  offered  hereby  involves a high
degree of risk.  Prospective  investors should carefully  consider the following
risk factors in addition to the other  information set forth and incorporated by
reference in this Prospectus  before making any decision to invest in the Common
Shares.

Accumulated  Deficit and  Uncertainty of Future  Profitability.  The Company was
originally  incorporated  in 1981. To date,  the Company's  sources of cash have
been the  proceeds  from the sale of its  stock  through  public  offerings  and
private  placements,  sales of  ADAGEN(R),  sales of  ONCASPAR(R),  sales of its
products  for  research  purposes,   contract  research  and  development  fees,
technology  transfer and license fees and royalty  advances.  At March 31, 1997,
the Company had an accumulated deficit of approximately  $108,636,000.  To date,
ADAGEN  and  ONCASPAR  are the only  products  of the  Company  which  have been
approved  for  marketing  by the FDA,  having  been  approved  in March 1990 and
February  1994,  respectively.  In 1993,  the  Company  granted  exclusive  U.S.
marketing rights for ONCASPAR to RPR in consideration  for which the Company has
received  an  aggregate  of  $6,000,000  of license  fees.  Under  this  license
agreement (the "Amended License  Agreement"),  the Company is entitled to a base
royalty of 23.5% until 2008.  During 1995,  RPR paid the Company  $3,500,000  in
advance  royalties.  Payments  of  base  royalties  under  the  Amended  License
Agreement will be offset against a credit in the original  amount of $5,970,000,
which  represents the royalty advance plus  reimbursement of certain amounts due
RPR under the original  agreement and interest expense.  Through March 31, 1997,
an aggregate of $2,073,000 in royalties  payable by RPR had been offset  against
the  original  credit.  ONCASPAR is also  currently  approved  for  marketing in
Germany and Russia.  The  Company  has granted  marketing  rights to ONCASPAR to
Medac for Europe and Russia.  Medac will  purchase  ONCASPAR from Enzon at a set
price  which  will  increase  over  the  term of the  marketing  agreement.  The
agreement  also contains  certain  minimum  purchase  requirements.  The Company
anticipates  moderate  growth of ONCASPAR  sales to RPR and Medac and  increased
royalties on RPR sales of ONCASPAR;  however, there can be no assurance that any
particular  sales level of ONCASPAR will be achieved or maintained.  The Company
intends to pursue future licensing,  marketing and development arrangements that
may result in additional  fees to the Company  prior to its  receiving  revenues
from  commercial  sales of its products  which are sufficient for the Company to
earn a profit. There can be no assurance, however, that the Company will be able
to  successfully  consummate any such  arrangements  or receive such fees in the
future.  Although  the  Company  has  been  receiving  reimbursement  from  most
third-party  payors for ADAGEN,  there can be no assurance that reimbursement at
these levels will  continue.  Lifetime  limits on benefits which are included in
most  private  health   insurance   policies  could  permit  insurers  to  cease
reimbursement   for  ADAGEN.   Potential   investors  should  be  aware  of  the
difficulties  a  biopharmaceutical  enterprise  such as the Company  encounters,
especially in view of the intense competition in the pharmaceutical  industry in
which the Company  competes.  There can be no assurance that the Company's plans
will either materialize or prove successful, that its products under development
will be  successfully  developed or that its  products  will  generate  revenues
sufficient to enable the Company to earn a profit.

Need for  Financing.  The  Company's  current  sources of liquidity are its cash
reserves,  and interest earned on such cash reserves,  sales of ADAGEN, sales of
ONCASPAR,  sales of its products for research purposes,  and license fees. There
can be no  assurance  as to the  level of sales of the  Company's  FDA  approved
products,  ADAGEN and  ONCASPAR,  or the amount of royalties  realized  from the
commercial sale of ONCASPAR pursuant to the

                                      - 5 -



Company's   license  with  RPR.  Total  cash  reserves,   including  short  term
investments,  as of March 31, 1997, were  approximately  $9,596,000.  Management
believes that the foregoing  sources of liquidity will be sufficient to meet the
Company's  anticipated cash requirements,  based on current spending levels, for
approximately the next two years. The Company's continued operations  thereafter
will depend upon its ability to (i) realize revenues from the commercial sale of
its products  which are  sufficient to cover its  operating and capital  expense
requirements, (ii) raise funds through equity or debt financing, or (iii) obtain
significant  contract  research and  development  fees or license  fees.  To the
extent the Company is unable to obtain funds,  it may be required to curtail its
activities or sell additional securities.  There can be no assurance that any of
the  foregoing  fund raising  activities  will  successfully  meet the Company's
anticipated cash needs.

Raw Materials and Dependence Upon Suppliers.  The Company is currently producing
many of the unmodified  compounds utilized in products it has under development,
including  purified  bovine  hemoglobin for use in its  PEG-hemoglobin  product.
There  can be no  assurance  that the  purified  bovine  hemoglobin  used in the
manufacture of PEG-hemoglobin can be produced in the amounts necessary to expand
the current  clinical  trials.  The  Company  may be  required to obtain  supply
contracts with outside suppliers for certain unmodified  compounds.  The Company
does not produce the unmodified  adenosine  deaminase used in the manufacture of
ADAGEN or the unmodified  L-asparaginase used in the manufacture of ONCASPAR and
has a supply  contract  with an outside  supplier  for each of these  unmodified
proteins.  Delays in obtaining or an inability to obtain any unmodified compound
which the Company does not produce,  including  unmodified  adenosine deaminase,
unmodified  L-asparaginase  or  unmodified  bovine  blood  could have a material
adverse effect on the Company. In the event the Company is required to locate an
alternate  supplier for an  unmodified  compound  utilized in a product which is
being sold  commercially or which is in clinical  development,  the Company will
likely be  required to do  additional  testing,  which  could  cause  delays and
additional  expenses,  to demonstrate that the alternate  supplier's material is
biologically  and chemically  equivalent to the unmodified  compound  previously
used. Such evaluations could include chemical, pre-clinical and clinical studies
and could delay  development  of a product  which is in clinical  trials,  limit
commercial  sales of an FDA  approved  product  and cause the  Company  to incur
significant  additional  expense.  Requirements  for such  evaluations  would be
determined by the stage of the product's  development and the reviewing division
of the FDA. If such alternate  material is not demonstrated to be chemically and
biologically  equivalent to the previously used unmodified compound, the Company
will likely be required to repeat some or all of the  pre-clinical  and clinical
trials conducted for such compound.  The marketing of an FDA approved drug could
be disrupted while such tests are conducted.  Even if the alternate  material is
shown to be  chemically  and  biologically  equivalent  to the  previously  used
compound,  the FDA may require the Company to conduct additional clinical trials
with such alternate material.

Patents and Proprietary Technology. The Company has licensed, and been issued, a
number of patents in the United States and other  countries and has other patent
applications pending to protect its proprietary technology. Although the Company
believes that its patents  provide  adequate  protection  for the conduct of its
business,  there can be no assurance  that such  patents will be of  substantial
protection  or  commercial  benefit to the  Company,  will  afford  the  Company
adequate protection from competing products,  will not be challenged or declared
invalid,  or that additional United States patents or foreign patent equivalents
will be issued to the Company. The degree of patent protection to be afforded to
biotechnological  inventions is uncertain and the Company's products are subject
to this  uncertainty.  The Company is aware of certain issued patents and patent
applications, and there may be other patents and patent applications, containing
subject matter which the Company or its licensees or  collaborators  may require
in order to research,  develop or  commercialize  at least some of the Company's
products. There can be no assurance that licenses under such subject matter will
be  available  on  acceptable  terms.  The  Company  expects  that  there may be
significant  litigation in the industry  regarding patents and other proprietary
rights  and,  if Enzon  were to become  involved  in such  litigation,  it could
consume a  substantial  amount of the  Company's  resources.  In  addition,  the
Company relies heavily on its proprietary  technologies for which pending patent
applications  have  been  filed  and on  unpatented  know-how  developed  by the
Company.  Insofar as the Company relies on trade secrets and unpatented know-how
to maintain its competitive  technological  position,  there can be no assurance
that  others may not  independently  develop  the same or similar  technologies.
Although the Company has taken steps to protect its trade secrets and unpatented
know-how, third-parties nonetheless may gain access to such information.

                                      - 6 -



Research  Corporation  Technologies,  Inc.  ("Research  Corporation")  held  the
original  patent  upon which the PEG  Process is based.  Research  Corporation's
patent in the United States and its patents in certain  foreign  countries  have
expired.  Although  the  Company has  obtained  several  improvement  patents in
connection  with the PEG Process  which it believes  represent  state of the art
technology,  there can be no assurance that any of these patents will enable the
Company to prevent infringement or that competitors will not develop competitive
products  outside the  protection  that may be afforded  by these  patents.  The
Company is aware that others have also filed patent  applications  and have been
granted  patents in the United  States and other  countries  with respect to the
application  of PEG to  proteins.  Based  upon the  expiration  of the  Research
Corporation  patent,  other  parties  will be  permitted  to make,  use, or sell
products covered by the claims of the Research  Corporation  patent,  subject to
other patents, including those held by the Company. The Company does not believe
that the  expiration  of the  Research  Corporation  patent will have a material
adverse  effect on the Company,  but there can be no assurance that this will be
the case.

Marketing Uncertainties and Dependence on Marketing Partners. Other than ADAGEN,
which the Company  markets on a worldwide  basis to a small patient  population,
the Company  does not engage in the direct  commercial  marketing  of any of its
products and therefore does not have an established  sales force. For certain of
its  products,  the  Company  has  provided  exclusive  marketing  rights to its
corporate partners in return for royalties to be received on sales. With respect
to ONCASPAR,  the Company has granted RPR  exclusive  marketing  rights in North
America and Medac exclusive  marketing rights in Europe and Russia.  The Company
expects to retain marketing partners to market ONCASPAR in other foreign markets
and is currently pursuing arrangements in this regard. There can be no assurance
that such discussions will result in the Company  concluding such  arrangements.
Regarding the marketing of certain of the Company's other future  products,  the
Company  expects to evaluate  whether to create a sales force to market  certain
products in the United States or to continue to enter into license and marketing
agreements with others for United States and foreign  markets.  These agreements
generally  provide that all or a  significant  portion of the marketing of these
products will be conducted by the Company's licensees or marketing partners.  In
addition, under certain of these agreements, the Company's licensee or marketing
partner may have all or a significant  portion of the development and regulatory
approval  responsibilities.  Should the  licensee or  marketing  partner fail to
develop a  marketable  product  (to the  extent it is  responsible  for  product
development) or fail to market a product successfully,  if it is developed,  the
Company's business may be adversely affected. There can be no assurance that the
Company's  marketing strategy will be successful.  Under the Company's marketing
and license agreements,  the Company's marketing partners and licensees may have
the right to terminate the agreement and abandon the product at any time for any
reason without  significant  payments.  The Company is aware that certain of its
marketing  partners are pursuing  parallel  development of products on their own
and with  other  collaborative  partners  which may  compete  with the  licensed
products  and there can be no  assurance  that the  Company's  other  current or
future marketing partners will not also pursue such parallel courses.

Reimbursement from Third-Party  Payors.  Sales of the Company's products will be
dependent in part on the availability of reimbursement from third-party  payors,
such as governmental health administration authorities,  private health insurers
and other organizations.  There can be no assurance that such reimbursement will
be  available  or will permit the Company to sell its  products at price  levels
sufficient for it to realize an appropriate  return on its investment in product
development.  Since  patients  who receive  ADAGEN will be required to do so for
their entire lives (unless a cure or another  treatment is developed),  lifetime
limits on benefits which are included in most private health insurance  policies
could permit insurers to cease reimbursement for ADAGEN.

Government  Regulation.   The  manufacturing  and  marketing  of  pharmaceutical
products in the United  States is subject to stringent  governmental  regulation
and the sale of any of the  Company's  products  for use in humans in the United
States  will  require  the  prior  approval  of the FDA.  Similar  approvals  by
comparable  agencies  are  required  in  most  foreign  countries.  The  FDA has
established  mandatory  procedures  and  safety  standards  which  apply  to the
clinical  testing,   manufacture  and  marketing  of  pharmaceutical   products.
Pharmaceutical  manufacturing  facilities are also regulated by state, local and
other authorities. Obtaining FDA approval for a new therapeutic may take several
years and involve  substantial  expenditures.  ADAGEN was approved by the FDA in
March 1990.  ONCASPAR was approved by the FDA in February 1994 and in Germany in
November 1994 for patients with

                                      - 7 -



acute  lymphoblastic   leukemia  who  are  hypersensitive  to  native  forms  of
L-asparaginase, and in Russia in April 1993 for therapeutic use in a broad range
of cancers.  Except for these  approvals,  none of the Company's  other products
have been approved for sale and use in humans in the United States or elsewhere.
There can be no  assurance  that the Company will be able to obtain FDA approval
for  any of  its  other  products.  Failure  to  obtain  requisite  governmental
approvals or failure to obtain approvals of the scope  requested,  will delay or
preclude the Company or its licensees or marketing partners from marketing their
products,  or limit the commercial  use of the products,  and thereby may have a
material adverse affect on the Company's liquidity and financial condition.

Intense  Competition and Risk of  Technological  Obsolescence.  Many established
biotechnology and pharmaceutical  companies with resources greater than those of
the Company are engaged in activities that are competitive  with Enzon's and may
develop  products  or  technologies  which  compete  with those of the  Company.
Although Enzon is not aware of any competitor  which has achieved the same level
as the Company in utilizing PEG technology in developing  drug  products,  it is
aware of other  companies  which are  engaged  in this field and there can be no
assurance that competitors  will not  successfully  develop such products in the
future.  Although  there are  other  companies  engaged  in the  development  of
Single-Chain  Antigen-Binding  (SCA(R))  proteins,  Enzon  believes  that  these
companies  will be  required  to obtain a license  under  Enzon's SCA patents in
order to  commercialize  any such product.  There can be no assurance,  however,
that this will prove to be the case. Rapid  technological  development by others
may result in the  Company's  products  becoming  obsolete  before  the  Company
recovers   a   significant   portion   of   the   research,    development   and
commercialization  expenses  incurred  with  respect  to those  products.  Enzon
believes  that the  experience  of  certain of its  personnel  in  research  and
development,  and its patents  and  proprietary  know-how  may provide it with a
competitive advantage in its field; however,  there can be no assurance that the
Company will be able to maintain such a competitive advantage,  should it exist,
in view of the greater  size and  resources  of many of its  competitors.  Other
drugs or  treatment  modalities  which are  currently  available  or that may be
developed  in the future,  and which treat the same  diseases as those which the
Company's  products are designed to treat, may be competitive with the Company's
products.

Potential Product Liability. The use of the Company's products during testing or
after  regulatory  approval  entails an inherent  risk of adverse  effects which
could  expose the Company to product  liability  claims.  The Company  maintains
product  liability  insurance  coverage in the total amount of  $10,000,000  for
claims  arising  from the use of its  products in clinical  trials  prior to FDA
approval and for claims arising from the use of its products after FDA approval.
There can be no assurance that the Company will be able to maintain its existing
insurance  coverage or obtain  coverage for the use of its other products in the
future.  Management  believes  that the  Company  maintains  adequate  insurance
coverage for the operation of its business at this time;  however,  there can be
no assurance that such insurance coverage and the resources of the Company would
be sufficient to satisfy any liability resulting from product liability claims.

Dividend  Policy and  Restrictions.  The  Company has paid no  dividends  on its
Common  Stock,  since its  inception  and does not plan to pay  dividends on its
Common  Stock in the  foreseeable  future.  Except as may be utilized to pay the
dividends  payable on the Company's  Series A Cumulative  Convertible  Preferred
Stock (the  "Series A  Preferred  Stock"),  any  earnings  which the Company may
realize will be retained to finance the growth of the Company. In addition,  the
terms of the Series A Preferred Stock restrict the payment of dividends on other
classes and series of stock.

Possible  Volatility  of Stock  Price.  Historically,  the  market  price of the
Company's  Common Stock has  fluctuated  over a wide range and it is likely that
the price of the  Common  Stock  will  fluctuate  in the  future.  Announcements
regarding technical innovations,  the development of new products, the status of
corporate collaborations and supply arrangements,  regulatory approvals,  patent
or proprietary  rights or other  developments  by the Company or its competitors
could have a significant impact on the market price of the Common Stock.

                                      - 8 -


                                 USE OF PROCEEDS

         The Company will not receive any  proceeds  from the sale of the Common
Shares offered herein by the Selling  Stockholders.  To date the Company has not
received  proceeds  from the  exercise  of the  Warrants.  If the  Warrants  are
exercised in their entirety the Company will receive estimated gross proceeds of
approximately  $2,625,000.  The Company intends to utilize any proceeds received
from the exercise of the Warrants for general corporate  purposes.  There can be
no assurance that the Warrants will be exercised.


                              SELLING STOCKHOLDERS

General

         Limited, one of the Selling Stockholders, purchased 1,094,890 shares of
Common  Stock and 40,000  shares of Series B  Preferred  Shares and was issued a
warrant for no separate consideration to purchase 638,686 shares of Common Stock
in the Private  Placement.  Limited converted the Series B Preferred shares into
2,030,456  shares of Common  Stock and has  previously  sold all such  shares of
Common Stock.  In addition,  Limited has previously  sold all but 595,157 of the
shares of Common  Stock  purchased  in the  Private  Placement.  Pursuant to the
Warrant Purchase Agreement,  Limited sold warrants to purchase 364,963 shares of
Common  Stock to the LLC.  The  595,157  shares  of  Outstanding  Common  Shares
purchased  in  the  Private  Placement,  the  638,686  Warrant  Shares  and  the
Additional  Shares to be issued upon the  occurrence  of a Triggering  Event are
being offered by the Selling Stockholders hereby.

         Pursuant to the  Certificate of  Designations  and/or the  Registration
Rights  Agreement,  the Company may be  required to issue  additional  shares of
Common Stock upon the  occurrence  of a Triggering  Event.  The  Certificate  of
Designations  Triggering Events include,  among other things, the failure of the
Company to file a registration  statement relating to the shares of Common Stock
issued upon conversion of the Series B Preferred Shares by a specified date, the
failure to maintain the  effectiveness  of the  registration  statement  for the
period  required,  or the failure of the Company to maintain  the listing of the
Common Stock on the Nasdaq  National  Market,  Nasdaq  Smallcap  Market or other
specified  national  securities  exchanges.  The  actual  number of shares to be
issued upon the occurrence of a Certificate of Designations  Triggering Event is
based on a formula contained in the Certificate of Designations which takes into
account the duration of the Triggering Event.

         Pursuant to the terms of the Registration Rights Agreement, the Company
may be required to issue an indeterminate  number of additional shares of Common
Stock  upon the  occurrence  of a  Registration  Rights  Triggering  Event.  The
Registration  Rights  Triggering  Events  are  substantially  identical  to  the
Certificate of Designations Triggering Events. Up to a maximum of 836,623 shares
of Common Stock to be issued upon the  occurrence  of a Triggering  Event may be
offered and sold by the Selling  Stockholders  pursuant hereto. In the event the
Company is required to issue more than  836,623  shares of Common Stock upon the
occurrence  of a  Triggering  Event,  the  Company  may be  required  to file an
additional registration statement to cover such additional shares.

         The Company has agreed to indemnify  the Selling  Stockholders  against
any liabilities,  under the Securities Act or otherwise, arising out of or based
upon  any  untrue  or  alleged  untrue  statement  of a  material  fact  in  the
Registration  Statement or this Prospectus or by any omission of a material fact
required to be stated therein except to the extent that such  liabilities  arise
out of or are based upon any untrue or alleged  untrue  statement or omission in
any information  furnished in writing to the Company by the Selling Stockholders
expressly for use in the Registration Statement.  Insofar as indemnification for
liabilities  arising  under the  Securities  Act may be permitted to  directors,
officers or persons  controlling  the Company  pursuant  to its  certificate  of
incorporation and by-laws,  the Company has been informed that in the opinion of
the Securities and Exchange  Commission such  indemnification  is against public
policy as expressed in the Act and is therefore unenforceable.


                                      - 9 -


         In  connection  with the  registration  of the  shares of Common  Stock
offered   hereby,   the  Company  will  supply   prospectuses   to  the  Selling
Stockholders.


Stock Ownership

         The table  below sets  forth (i) the  number of shares of Common  Stock
owned  beneficially by the Selling  Stockholders prior to the Offering (assuming
no shares are issued upon the  occurrence of a  Registration  Rights  Triggering
Event);  (ii) the number of shares of Common Stock being  offered by the Selling
Stockholders  pursuant to this Prospectus;  (iii) the number of shares of Common
Stock to be owned  beneficially by the Selling  Stockholders after completion of
the offering,  assuming that all of the Common Shares  offered  hereby are sold;
and (iv) the  percentage of the  outstanding  shares of Common Stock to be owned
beneficially  by the Selling  Stockholders  after  completion  of the  offering,
assuming that all of the Common Shares offered  hereby are sold.  Other than the
transactions  described  herein,  the  Selling  Stockholders  have  not  had any
material relationship with the Company during the past three years.

Number of Percentage of Shares to be Outstanding Shares Number of Owned of Common Stock Shares Beneficially to be Owned Beneficially Number of After Beneficially After Owned Prior Shares Completion Completion Selling Stockholders to Offering Offered of Offering of Offering(1) Clearwater Fund IV Limited 2,359,108(2) 868,880(4) 2,096,228 6.67% Clearwater Fund IV LLC 440,463(3) 364,963(4) 75,500 *
(1) Based upon shares of Common Stock outstanding as of August 1, 1997. (2) Does not include shares to be issued upon the occurrence of a Triggering Event, if any. Includes 272,723 shares to be issued upon exercise of the Warrants. (3) Does not include shares to be issued upon the occurrence of a Triggering Event, if any. Includes 364,963 shares to be issued upon exercise of the Warrants. (4) Does not include shares to be issued upon the occurrence of a Triggering Event, if any. * Less than 1%. PLAN OF DISTRIBUTION The Common Shares may be sold pursuant to this Prospectus by the Selling Stockholders. These sales may occur in privately negotiated transactions or in the over-the-counter market through brokers and dealers as agents or to brokers and dealers as principals, who may receive compensation in the form of discounts or commissions from the Selling Stockholders or from the purchasers of the Common Stock for whom the broker-dealers may act as agent or to whom they may sell as principal, or both. The Company has been advised by the Selling Stockholders that they have not made any arrangements relating to the distribution of the shares of Common Stock covered by this Prospectus. In effecting sales, broker-dealers engaged by the Selling Stockholders may arrange for - 10 - other broker-dealers to participate. Broker-dealers will receive commissions or discounts from the Selling Stockholders in amounts to be negotiated immediately prior to the sale. The Selling Stockholders and any broker-dealers who execute sales for the Selling Stockholders may be deemed to be "underwriters" within the meaning of the Securities Act by virtue of the number of shares of Common Stock to be sold or resold by such persons or entities or the manner of sale thereof, or both. If the Selling Stockholders, broker-dealers or other holders were determined to be underwriters, any discounts or commissions received by them or by brokers or dealers acting on their behalf and any profits received by them on the resale of their shares of Common Stock might be deemed underwriting compensation under the Securities Act. The Selling Stockholders have represented to the Company that any purchase or sale of the Common Stock by it will be in compliance with applicable rules and regulations of the Commission. LEGAL MATTERS The legality of the shares of Common Stock offered hereby has been passed on for the Company by Ross & Hardies, New York, New York. EXPERTS The consolidated financial statements of Enzon, Inc. and subsidiaries as of June 30, 1996 and 1995 and for each of the years in the three-year period ended June 30, 1996, have been incorporated by reference herein and in the Registration Statement in reliance upon the report of KPMG Peat Marwick LLP, independent certified public accountants, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing. - 11 - PART II INFORMATION NOT REQUIRED IN PROSPECTUS Item 14. Other Expenses of Issuance and Distribution The following table sets forth an itemized estimate of fees and expenses payable by the Registrant in connection with the offering of the securities described in this registration statement, other than underwriting discounts and commissions. SEC registration fee................................................. $ 0* Legal fees and expenses............................................... $20,000 Accounting fees and expenses.......................................... $ 5,500 Miscellaneous......................................................... $ 5,000 Total..................................... $ 30,500 ======== * A filing fee of $7,145 was paid upon the initial filing of this registration statement. Item 15. Indemnification of Directors and Officers The General Corporation Law of the State of Delaware provides for indemnification as set forth in Section 145 thereof. The Registrant's By-laws, as amended provide for indemnification of the directors and officers of the Registrant against all costs, expenses and amounts of liability incurred by them in connection with any action, suit or proceeding in which they are involved by reason of their affiliation with the Registrant, to the fullest extent permitted by law. The Registrant's directors and officers also have indemnification agreements with the Company, which expand the indemnification protection provided to them under the Company's By-laws. On January 20, 1987, the stockholders approved an amendment to the Registrant's Certificate of Incorporation which added a new Article 10 limiting the liability to the Registrant of individual directors for breach of their fiduciary duty of care to the Registrant. The effect of this amendment is to eliminate liability of directors for monetary damage arising out of negligent or grossly negligent conduct, including such conduct in acquisition transactions. However, liability of directors under the federal securities laws will not be affected. Item 16. Exhibits
Page Number or Exh. Incorporation Number Description By Reference 5.1 Opinion of Ross & Hardies regarding legality E-1 23.1 Consent of Ross & Hardies (contained in opinion filed as Exhibit 5.1) 23.2 Consent of KPMG Peat Marwick LLP E-3 24.0 Power of Attorney +
+ Powers of attorney are contained in signatures of original filing. II-1 Item 17. Undertakings The undersigned Registrant hereby undertakes: (1) to file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement: (i) To include any prospectus required by Section 10(a) (3) of the Securities Act of 1933; (ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement; notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in the volume and price represent no more than a 20% change in the maximum aggregate offering price set forth in the "Calculation of Registration Fee" table in the effective registration statement. (iii)To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement: Provided, however, that paragraphs (1)(i) and (1)(ii) do not apply if the registration statement is on Form S-3 or Form S-8, and the information required to be included in a post-effective amendment by those paragraphs is contained in the periodic reports filed by the Registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement. (2) That, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. (3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering. (4) That, for purposes of determining any liability under the Securities Act of 1933, each filing of the Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and where applicable, each filing of an employee benefit plan's annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in this Registration Statement shall be deemed to be a new Registration Statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. (5) Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the Registrant pursuant to the foregoing provisions or otherwise, the Registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue. II-2 SIGNATURES Pursuant to the requirements of the Securities Act of 1933, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized in the City of Piscataway, State of New Jersey, on August 12, 1997. ENZON, INC. By: /s/PETER G. TOMBROS Peter G. Tombros, President and Chief Executive Officer Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated. Signature Capacity Date /s/PETER G. TOMBROS President, Chief August 12, 1997 - ------------------------- Peter G. Tombros Executive Officer and Director (Principal Executive Officer) /s/RANDY H. THURMAN* Chairman of the Board August 12, 1997 - ----------------------- Randy H. Thurman /s/KENNETH J. ZUERBLIS Vice President - August 12, 1997 - ------------------------- Kenneth J. Zuerblis Finance and Chief Financial Officer (Principal Financial Officer and Principal Accounting Officer) /s/ROSINA B. DIXON* Director August 12, 1997 - ------------------------- Rosina B. Dixon /s/ROBERT LEBUHN* Director August 12, 1997 Robert LeBuhn /s/A.M. "DON" MACKINNON* Director August 12, 1997 - ------------------------ A.M. "Don" MacKinnon * Signed by Kenneth J. Zuerblis, as attorney-in-fact. ENZON, INC. EXHIBIT INDEX Exhibit No. Description 5.1 Opinion of Ross & Hardies 23.2 Consent of KPMG Peat Marwick LLP SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 --------------- EXHIBITS TO FORM S-3 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 --------------- ENZON, INC. (Exact name of registrant as specified in its charter)

                                                                     EXHIBIT 5.1


                                            [ROSS & HARDIES LETTERHEAD]


                                                  August 12, 1997


Enzon, Inc.
20 Kingsbridge Road
Piscataway, New Jersey 08854

             Re:      Registration Statement on Form S-3

Ladies and Gentlemen:

          You have  requested  our opinion with respect to the  registration  by
Enzon,  Inc. (the  "Company")  pursuant to a Registration  Statement on Form S-3
(the "Registration Statement") under the Securities Act of 1933, as amended (the
"Act"),  of an aggregate of 2,070,466 shares of the Company's Common Stock, $.01
par  value per share  (the  "Common  Stock"),  including  595,157  shares of the
outstanding  Common Stock (the "Outstanding  Common Shares"),  638,686 shares of
Common Stock issuable upon the exercise of outstanding warrants (the "Warrants")
and up to 836,623 shares of Common Stock issuable upon the occurrence of certain
triggering  events (herein a "Triggering  Event")  specified in the Registration
Rights Agreement (the "Registration  Rights Agreement") dated March 15, 1996, by
and among the Company and the other parties thereto.

          In so acting,  we have  examined  originals  or copies,  certified  or
otherwise identified to our satisfaction, of such documents,  corporate records,
certificates of public  officials and other  instruments and have conducted such
other investigations of fact and law as we have deemed relevant and necessary to
form a  basis  for  the  opinions  hereinafter  expressed.  In  conducting  such
examination,  we have assumed (i) that all signatures are genuine, (ii) that all
documents and instruments  submitted to us as copies conform with the originals,
and (iii) the due execution  and delivery of all  documents  where due execution
and delivery are a prerequisite to the  effectiveness  thereof.  As to any facts
material to this opinion,  we have relied upon statements and representations of
officers and other  representatives  of the Company and  certificates  or public
officials and have not independently verified such facts.

          Based  upon the  foregoing,  it is our  opinion  that the  Outstanding
Common Shares are validly  issued,  fully paid and  non-assessable  and that the
Common Stock issuable upon the proper  exercise of the Warrants  and/or upon the
occurrence  of a  Triggering  Event  will be  validly  issued,  fully  paid  and
non-assessable  when issued in accordance with the terms of such Warrants or the
Registration Rights Agreement.

          We express no  opinion as to the laws of any  jurisdiction  other than
the State of New York and the United States of America. Insofar as the foregoing
opinion relates to matters that would be controlled by the  substantive  laws of
any  jurisdiction  other than the  United  States of America or the State of New
York, we have assumed that the substantive laws of such jurisdiction  conform in
all respects to the internal laws of the State of New York.


                                                        E-1





          We hereby  consent to the  reference  to our firm in the  Registration
Statement relating to the registration of 2,070,466 shares of Common Stock.

                                                      Very truly yours,

                                                      ROSS & HARDIES


                                                         By: /s/KEVIN T. COLLINS
                                                         -----------------------
                                                                Kevin T. Collins
                                                                       A Partner

                                                        E-2


                                                                    EXHIBIT 23.2





                                           INDEPENDENT AUDITORS' CONSENT



The Board of Directors
Enzon, Inc.


We consent to the use of our reports incorporated herein by reference and to the
reference to our firm under the heading "Experts" in the prospectus.



                                                        /s/KPMG PEAT MARWICK LLP
                                                        ------------------------
                                                           KPMG Peat Marwick LLP


Short Hills, New Jersey
August 12, 1997


                                       E-3