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

                                September 7, 2004
                  --------------------------------------------
                                 Date of Report
                        (Date of earliest event reported)

                               ZYMOGENETICS, INC.
- --------------------------------------------------------------------------------
               (Exact Name of Registrant as Specified in Charter)

             Washington                   000-33489               91-1144498
- --------------------------------------------------------------------------------
    (State or Other Jurisdiction    (Commission File No.)        (IRS Employer
         of Incorporation)                                  Identification No.)

            1201 Eastlake Avenue East, Seattle, Washington 98102-3702
- --------------------------------------------------------------------------------
          (Address of Principal Executive Offices, including Zip Code)

                                 (206) 442-6600
- --------------------------------------------------------------------------------
              (Registrant's Telephone Number, Including Area Code)


- --------------------------------------------------------------------------------
          (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))


                                       1


Item 1.01.        Entry into Material Definitive Agreement.

     On September 7, 2004, ZymoGenetics, Inc. issued a press release announcing
it entered into a master agreement with Serono S.A. and Serono B.V. (together,
"Serono"), dated September 7, 2004 (the "Master Agreement") providing for a
strategic research, development and commercialization alliance with Serono. The
terms of the Master Agreement and related agreements are subject to review by
the United States Federal Trade Commission and Department of Justice, under the
provisions of the Clayton Act, 15 U.S.C. ss. 18a, as added by the
Hart-Scott-Rodino Antitrust Improvements Act of 1976. The press release is
attached hereto as Exhibit 99.1 and is incorporated herein by reference.

     In August 2001, ZymoGenetics entered into a collaborative development and
marketing agreement with Ares Trading S.A., a wholly owned subsidiary of Serono
S.A., focused on two preclinical product candidates, designated TACI and BCMA,
that are involved in the regulation of the human immune system. During the term
of the agreement, ZymoGenetics and Serono will work together exclusively to
develop biopharmaceutical products based on the two receptors for the treatment
of autoimmune diseases. Together with Serono, ZymoGenetics completed a Phase 1
clinical trial of TACI-Ig in healthy volunteers in early 2004. The companies are
currently conducting ongoing Phase 1 clinical trials of TACI-Ig in systemic
lupus erythematosus and rheumatoid arthritis patients.

Item 3.02.        Unregistered Sales of Equity Securities.

     Pursuant to the Master Agreement, at the closing of the transaction
ZymoGenetics will issue and sell to Serono 3,176,620 shares of ZymoGenetics
common stock at a price per share of $15.74, for an aggregate purchase price of
approximately $50 million. The actual purchase price per share and number of
shares to be issued are subject to certain market-based adjustments. The shares
that Serono will purchase will be exempt from registration pursuant to Rule 506
of the Securities Act because Serono is an "accredited investor" as defined in
Rule 501(a) of Regulation D of the Securities Act. For purposes of the
exemption, ZymoGenetics will rely on Serono's representations and warranties
made pursuant an agreement executed in connection with the closing that Serono
is an "accredited investor."

Item 9.01.        Financial Statements and Exhibits.

         (c)      99.1     Press Release issued September 7, 2004.


                                       2


                                    SIGNATURE


 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.

                                         ZYMOGENETICS, INC.



Dated:  September 10, 2004               By    /s/ James A. Johnson
                                               ---------------------------------
                                               James A. Johnson
                                               Chief Financial Officer


                                       3





                                  Exhibit Index

         99.1     Press Release issued September 7, 2004.

                                       4