UNITED STATES

                       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): September 1, 2004
                                                        -----------------

                               CYTOGEN CORPORATION
         --------------------------------------------------------------
               (Exact Name of Registrant as Specified in Charter)

         Delaware                       000-14879                 22-2322400
----------------------------     ------------------------    -------------------
(State or Other Jurisdiction     (Commission File Number)      (I.R.S. Employer
     of Incorporation)                                       Identification No.)

 650 College Road East, CN 5308, Suite 3100, Princeton, NJ            08540
--------------------------------------------------------------    --------------
                   (Address of Principal Executive Offices)         (Zip Code)

       Registrant's telephone number, including area code: (609) 750-8200
                                                           --------------

--------------------------------------------------------------------------------
         (Former Name or Former Address, if Changed Since Last Report)

     Check the  appropriate  box below if the Form 8-K  filing  is  intended  to
simultaneously  satisfy the filing obligation of the registrant under any of the
following provisions (see General Instruction A.2. below):

     |_| Written  communications  pursuant to Rule 425 under the  Securities Act
(17 CFR 230.425)

     |_| Soliciting  material pursuant to Rule 14a-12 under the Exchange Act (17
CFR 240.14a-12)

     |_| Pre-commencement  communications  pursuant to  Rule 14d-2(b)  under the
Exchange Act (17 CFR 240.14d-2(b))

     |_| Pre-commencement  communications  pursuant to  Rule 13e-4(c)  under the
Exchange Act (17 CFR 240.13e-4(c))



ITEM 3.03  MATERIAL MODIFICATION TO RIGHTS OF SECURITY HOLDERS.

     Effective  September  1, 2004,  American  Stock  Transfer  & Trust  Company
("AST"),  located at 59 Maiden Lane, Plaza Level, New York, NY 10038,  telephone
number (718) 921-8200, was appointed as the new registrar and transfer agent for
Cytogen  Corporation  (the "Company"),  replacing  Mellon Investor  Services LLC
("Mellon").

     In connection with the Company's engagement of AST, the Company executed an
Agreement for  Substitution and Amendment of Rights Agreement with AST, dated as
of September 1, 2004 (the  "Substitution  Agreement"),  pursuant to which, among
other  things,  AST shall  replace  Mellon as rights  agent under the  Company's
Rights Agreement, as amended to date.

     The full text of the  Substitution  Agreement is attached hereto as Exhibit
4.1 to this Current Report on Form 8-K and is incorporated  herein by reference.
The  foregoing  description  of the  Substitution  Agreement is qualified in its
entirety by reference to such Exhibit.

ITEM 9.01  FINANCIAL STATEMENTS AND EXHIBITS

(c)  Exhibits.

     Exhibit No.       Description
     -----------       -----------

        4.1            Agreement   for  Substitution  and  Amendment  of  Rights
                       Agreement by and between the Company and  American  Stock
                       Transfer & Trust Company dated as of September 1, 2004.





                                   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.

                                                CYTOGEN CORPORATION



                                                By: /s/ Michael D. Becker
                                                   -----------------------------
                                                   Michael D. Becker
                                                   President and Chief Executive
                                                   Officer

Dated:   September 2, 2004






                                  EXHIBIT INDEX


       Exhibit No.       Description
       -----------       -----------
           4.1           Agreement for  Substitution  and  Amendment  of  Rights
                         Agreement by and between the Company and American Stock
                         Transfer & Trust Company dated as of September 1, 2004.