SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) June 28,  1999

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

Delaware                        0-12957                22-2372868
(State or other jurisdiction         (Commission             (IRS Employer
or incorporation)               File Number)           Identification)

20 Kingsbridge Road, Piscataway, New Jersey                 08854
(Address of principal executive offices)                  (Zip Code)

Registrant's telephone number, including area code         (732) 980-4500

--------------------------------------------------------------------------------
(Former name or former address, if changed since last report)

Item 5. Other Events

Enzon, Inc. ("Enzon") and Schering-Plough  Corporation  ("Schering-Plough")
revised their 1990  PEG-INTRON  licensing  agreement,  which  entitled  Enzon to
royalties  for  product  sales and  specific  milestone  payments.  The  revised
agreement calls for  Schering-Plough to pay Enzon royalties on sales at a higher
effective  rate than provided for in the original  agreement in exchange for the
return to Schering-Plough of Enzon's exclusive U.S. manufacturing rights for the
product.

Additionally,   the  revised   agreement   grants  to   Schering-Plough   a
non-exclusive  worldwide  license,  with a limited  right to  sublicense,  under
Enzon's patents covering another form of PEG called "Branched PEG," which uses a
different proprietary PEG technology than PEG-INTRON.  The patent Enzon licensed
to Schering-Plough is the subject of a patent infringement suit brought by Enzon
against Shearwater Polymers, Inc. earlier this year.

PEG-INTRON  is a modified  form of  Schering-Plough's  INTRON A (interferon
alfa-2b,  recombinant)  that was developed  using Enzon's PEG technology to have
longer-acting  properties.  Schering-Plough  is continuing  its  development  of
PEG-INTRON as a monotherapy  for the treatment of hepatitis C, which is in Phase
III  clinical  trials that began in July 1997.  PEG-INTRON  is also in Phase III
clinical  trials  as  combination  therapy  with  REBETOL  (ribavirin,  USP) for
hepatitis C. In  addition,  PEG-INTRON  is in Phase III clinical  trials for two
cancer indications, malignant

melanoma  and  chronic  myelogenous  leukemia  (CML),  as well as in early stage
trials for various solid tumors.

Certain  information  included  in this  report  contains  forward  looking
statements  made  pursuant to the Private  Securities  Litigation  Reform Act of
1995.  Such  statements  are  based  on  assumptions  that  Enzon  believes  are
reasonable,  but are  subject  to a wide range of risks and  uncertainties  and,
therefore,  there  can be no  assurance  that  actual  results  may  not  differ
materially from those expressed or implied by such  forward-looking  statements.
Factors that could cause actual results to differ materially,  including but not
limited to, risks in obtaining and maintaining  regulatory approval for expanded
indications,  market  acceptance of and continuing  demand for Enzon's products,
the impact of  competitive  products  and  pricing and other  factors  which are
described in Enzon's SEC filings,  including  Enzon's  Report on Form 10-K dated
June 30, 1998, and Reports on Form 10-Q dated  September 30, 1998,  December 31,
1998, and March 31, 1999, incorporated herein by reference.

SIGNATURES

Pursuant to the  requirements  of the Securities  Exchange Act of 1934, the
Registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned hereunto duly authorized.

Dated: July 13, 1999

ENZON, INC.
(Registrant)

By: /s/ KENNETH J. ZUERBLIS
-----------------------------
Kenneth J. Zuerblis
Vice President, Finance
and Chief Financial  Officer