As of May 15, 1995


Mr. Peter G. Tombros
159 Lambert Road
New Canaan, CT  06840


      Re:  AMENDMENT TO EMPLOYMENT AGREEMENT

Dear Peter:

      This  letter  agreement, when signed  by  you,  will  serve  as  a  first
amendment to your employment  agreement  with Enzon, Inc. (the "Company") dated
as of March 25, 1994 (the "Employment Agreement").

      Pursuant to Section 3(b) of the Employment Agreement, you are entitled to
receive an award (the "Award") under the Company's  Total  Compensation Program
for Officers and Senior Executives (the "Program") based on  the  completion of
your  first  year  of  employment  with  the Company.  The Employment Agreement
further provides that the Award is to consist  of  an  option granted under the
Company's  Non-Qualified  Stock Option Plan (the "Plan") and  cash  having  the
value and based on the terms set forth therein.

      This will confirm our  agreement  that you will not receive the Award for
the completion of your first year of employment with the Company as provided in
Section 3(b) of the Employment Agreement,  and  in  lieu  thereof,  the Company
shall  grant to you an option (the "Option") under the Plan to purchase  84,000
shares of the Company's common stock, $.01 par value (the "Common Stock").  The
exercise  price  per  share  of  Common Stock shall be $2.00, which is the fair
market value of a share of Common  Stock  on the date hereof.  The Option shall
be exercisable as to 42,000 shares on May 15,  1996  and  as  to  the remaining
42,000  shares on May 15, 1997 and shall terminate in its entirety on  May  15,
2005.  The  Option  is  not  being  granted pursuant to the Program.  Except as
provided herein, the Employment Agreement shall remain unchanged.

      To  evidence your agreement to the  foregoing,  kindly  countersign  this
letter on the line provided below.


                                          Very truly yours,

                                          ENZON, INC.
                                          By:/S/ KENNETH J. ZUERBLIS
                                          Name: Kenneth J. Zuerblis
                                          Title: Vice President, Finance


AGREED AND ACCEPTED


/S/ PETER G. TOMBROS
Peter G. Tombros



                                      E1