<PAGE>
 
                      SECURITIES AND EXCHANGE COMMISSION    Conformed
                            Washington, D.C. 20549             Copy

                                   FORM 10-Q/A
                  (Mark One)
                  [X]  QUARTERLY REPORT PURSUANT TO SECTION 13
                       OR 15(d) OF THE SECURITIES EXCHANGE ACT 
                       OF 1934

                  For the quarterly period ended June 30, 1996
                                                 -------------
                                      OR

                  [_]  TRANSITION REPORT PURSUANT TO SECTION 13
                       OR 15(d) OF THE SECURITIES EXCHANGE ACT
                       of 1934

                  For the transition period from         to           
                                                 --------  ---------

                        Commission file number 0-14879
                                               -------
                              Cytogen Corporation
             ------------------------------------------------------
             (Exact name of Registrant as specified in its charter)

        Delaware                                     22-2322400
-------------------------------                  ---------------------
(State or Other Jurisdiction of                    (I.R.S. Employer
Incorporation or Organization)                   Identification Number)

           600 College Road East, CN 5308, Princeton, NJ  08540-5308
           ---------------------------------------------------------
            (Address of Principal Executive Offices and Zip Code)

       Registrant's telephone number, including area code (609) 987-8200

     Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days : Yes X No .
                                           ---      ---

     Indicate the number of shares outstanding of each of the issuer's classes 
of common stock, as of the latest practicable date:

          Class                                   Outstanding at July 24, 1996
----------------------------                      ----------------------------
Common Stock, $.01 par value                                 47,925,175


Warrants to Purchase One Share of Common Stock,               4,023,495
          $.01 par value


<PAGE>
 

Item 6 -  Exhibits and Reports on Form 8-K
------  
             (a) Exhibits:
           
              3.-  Certificate of Incorporation of CYTOGEN Corporation.

             10.1- Second Amendment to the License Agreement between CYTOGEN 
                   Corporation and The Dow Chemical Company dated May 20,
                   1996.*

             10.2- Amendment No. 1 to the CYTOGEN Corporation 1995 Stock
                   Option Plan dated May 22, 1996.

             10.3- Amendment No. 2 to the CYTOGEN Corporation 1988 Stock
                   Option Plan for Non-Employee Directors dated May 22, 1996.

             27-   Financial Data Schedule (Submitted to SEC only in electronic 
                   format).

*    CYTOGEN Corporation has requested confidential treatment of certain
     provisions contained in this exhibit. The copy filed as an exhibit omits
     the information subject to the confidentiality request. This exhibit
     expands the licensed field thereunder to include osteoblastic diseases,
     including rheumatoid arthritis.

             (b)   Reports on Form 8-K:

             None

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<PAGE>
 
                                  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 thereunto duly authorized.


                                         CYTOGEN CORPORATION


    
Date October 2, 1996                     By /s/ T. Jerome Madison
     ----------------------------        ---------------------------------
                                         T. Jerome Madison
                                         Chief Financial Officer
                                         (Authorized Officer and Principal 
                                         Financial Officer)



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