<PAGE>

                                                                  EXHIBIT 3.02

                                 STATE OF DELAWARE


                                    [SEAL]


                           OFFICE OF SECRETARY OF STATE

                               ------------------

     I, MICHAEL HARKINS, SECRETARY OF STATE OF THE STATE OF DELAWARE, DO HEREBY
CERTIFY THE ATTACHED IS A TRUE AND CORRECT COPY OF THE CERTIFICATE OF
AMENDMENT OF "CHIRON CORPORATION" FILED IN THIS OFFICE ON THE TWELFTH DAY OF
DECEMBER, A.D. 1991, AT 11:24 O'CLOCK A.M.

                              * * * * * * * * * * *




[SEAL]

                                            /s/Michael Harkins
                                            -----------------------------------
                                            Michael Harkins, Secretary of State

                                            AUTHENTICATION: #3267833

                                                      DATE: 12/12/1991




<PAGE>

                           CERTIFICATE OF AMENDMENT
                                       OF
                     RESTATED CERTIFICATE OF INCORPORATION

     CHIRON CORPORATION, a corporation organized and existing under and by
virtue of the General Corporation Law of the State of Delaware,

     DOES HEREBY CERTIFY:

     FIRST: That at a meeting of the Board of Directors of CHIRON
CORPORATION, resolutions were duly adopted setting forth a proposed amendment
of the Restated Certificate of Incorporation of said corporation, declaring
said amendment to be advisable and calling a meeting of the stockholders of
said corporation for consideration thereof. The resolution setting forth the
proposed amendment is as follows:

     RESOLVED, that the Restated Certificate of Incorporation of this
corporation be amended by changing the Article thereof numbered "FIFTH" so
that, as amended, said Article shall be and read as follows:

     "FIFTH: This corporation is authorized to issue two classes of shares to
be designated, respectively, `Preferred Stock' and `common stock.' The total
number of shares which this corporation is authorized to issue is one hundred
five million (105,000,000). Five million (5,000,000) shares shall be
Preferred Stock and one hundred million (100,000,000) shares shall be common
stock. The Preferred Stock shall have a par value of $0.01 per share; the
common stock shall have a par value of $0.01 per share.

     1.    PREFERRED STOCK.

           The Preferred Stock may be issued from time to time in one or more
      series. The Board of Directors is expressly authorized, in the
      resolution or resolutions providing for the issuance of any wholly
      unissued series of Preferred Stock, to fix, state and express the
      powers, rights, designations, preferences, qualifications, limitations
      and restrictions thereof, including without limitation: the rate of
      dividends upon which and the times at which dividends of shares of such
      series shall be payable and the preference, if any, which such
      dividends shall have relative to dividends on shares of any other class
      or classes or any other series of stock of the corporation; whether
      such dividends shall be cumulative or noncumulative, and if cumulative,
      the date or dates from which dividends on shares of such series shall
      be cumulative; the voting rights, if any, to be provided for shares of
      such series: the rights, if any, which the holders of shares of such
      series shall have in the event of any voluntary or involuntary
      liquidation, dissolution or winding up of the affairs of the
      corporation; the rights, if any, which the holders of shares of such
      series shall have to convert such shares into or exchange such shares
      for shares of stock of the corporation, and the terms and conditions,
      including price and rate of exchange of such conversion or

<PAGE>

      exchange; and the redemption rights (including sinking fund provisions),
      if any, for shares of such series; and such other powers, rights,
      designations, preferences, qualifications, limitations and restrictions
      as the Board of Directors may desire to so fix. The Board of Directors
      is also expressly authorized to fix the number of shares constituting
      such series and to increase or decrease the number of shares of any
      series prior to the issuance of shares of that series and to increase
      or decrease the number of shares of any series subsequent to the
      issuance of shares of that series, but not to decrease such number
      below the number of shares outstanding. In case the number of shares of
      any series shall be so decreased, the shares constituting such decrease
      shall resume the status which they had prior to the adoption of the
      resolution originally fixing the number of shares of such series.

     2.    COMMON STOCK.

          The common stock may be issued from time to time in one or more
     series. Ninety-nine million five hundred thousand (99,500,000) shares of
     common stock are designated `Common Stock.' All other series of common
     stock shall collectively consist of five hundred thousand (500,000) shares
     and shall be designated, as a group, `Restricted Common Stock.'

     3.    RESTRICTED COMMON STOCK.

           (a)  AUTHORITY OF BOARD TO FIX RIGHTS OF RESTRICTED COMMON STOCK.
     The Board of Directors is expressly authorized, in the resolution or
     resolutions providing for the issuance of any wholly unissued series of
     Restricted Common Stock, to fix, state and express, within the limits
     expressed hereinbelow, the powers, designations, preferences and rights
     of the Restricted Common Stock, and the qualifications, limitations or
     restrictions thereof. The Board of Directors is also expressly
     authorized to fix the number of shares constituting such series and to
     increase or decrease the number of shares of any series prior to the
     issuance of shares of that series and to increase or decrease the number
     of shares of any series subsequent to the issue of shares of that
     series, but not to decrease such number below the number of such series
     then outstanding. In case the number of shares of any series shall be so
     decreased, the shares constituting such decrease shall resume the status
     which they had prior to the adoption of the resolution originally fixing
     the number of shares of such series.

           (b)  SPECIFIC RIGHTS. The rights, preferences, privileges and
     restrictions of the Common Stock and Restricted Common Stock shall be
     identical in all respects, except as follows, or, for the Restricted
     Common Stock, as fixed and determined by the Board of Directors within
     the limitations which follow:

                i)   CONVERSION RIGHTS. The Restricted Common Stock may be
     convertible into or exchangeable for Common Stock, at a conversion or

                                      2.

<PAGE>

     exchange ratio of not more than one share of Common Stock for each share
     of Restricted Common Stock and upon such other terms and conditions as
     the Board of Directors may establish.

                ii)  VOTING RIGHTS. Subject to the special voting rights (if
     any) of the Preferred Stock set forth or determined as provided in
     this Article FIFTH, each holder of Common Stock of this corporation
     shall be entitled to one vote for each share of such stock outstanding
     in the name of such holder on the books of this corporation on the
     record date designated for the purpose of such vote, and each holder of
     Restricted Common Stock of the corporation shall be entitled, for each
     share of such Restricted Common Stock outstanding in the name of such
     holder on the books of the corporation on the record date designated for
     the purpose of such vote, to the number of votes as has been fixed by
     the Board of Directors, but the vote per share of Restricted Common
     Stock shall not be more than the proportionate vote of the Common Stock
     into which such Restricted Common Stock is convertible or exchangeable.

                iii) DIVIDEND RIGHTS. Subject to the prior rights (if any)
     of the holders of the Preferred Stock as to dividends, the holders of
     outstanding shares of Common Stock and Restricted Common Stock shall be
     entitled to receive, when and as declared by the Board of Directors, out
     of the assets of the corporation at the time legally available therefor,
     dividends at the rate determined by the Board of Directors: provided,
     however, that the dividend on each share of Restricted Common Stock
     shall be less than the proportionate dividend on each share of Common
     Stock into which it is convertible or exchangeable.

                iv)  LIQUIDATION RIGHTS. In the event of any liquidation,
      dissolution or winding up of this corporation either voluntarily or
     involuntarily, but subject to the liquidation preference (if any) of the
     holders of Preferred Stock by reason of their ownership thereof, the
     holders of Common Stock and Restricted Common Stock shall be entitled to
     receive pro rata the remaining assets of the corporation available for
     distribution to shareholders except that the amounts per share paid in
     liquidation on each share of Restricted Common Stock shall be less than
     the proportionate amount per share paid on each share of the Common
     Stock into which it is convertible or exchangeable.

                v)   ADJUSTMENTS. The Board of Directors shall make
     appropriate adjustments to the conversion or exchange ratio and to
     the voting, dividend and liquidation rights of the Restricted Common
     Stock in the event of any stock split, stock dividend or similar
     transaction affecting the number of outstanding shares of Common Stock
     or Restricted Common Stock without the corporation's receipt of
     consideration thereof."

                                     3.

<PAGE>

     SECOND: That thereafter, pursuant to resolution of its Board of
Directors, a special meeting of the stockholders of said corporation was duly
called and held, upon notice in accordance with Section 222 of the General
Corporation Law of the State of Delaware at which meeting the necessary
number of shares as required by statute were voted in favor of the amendment.

     THIRD: That said amendment was duly adopted in accordance with the
provisions of Section 242 of the General Corporation Law of the State of
Delaware.

     IN WITNESS WHEREOF, said CHIRON CORPORATION has caused this certificate
to be signed by EDWARD E. PENHOET, its Vice Chairman of the Board of
Directors and Chief Executive Officer, and attested by WILLIAM G. GREEN, its
Secretary, this 12th day of December, 1991.



                                               By  /s/Edward E. Penhoet
                                                   --------------------------
                                                   Edward E. Penhoet
                                                   Vice Chairman and
                                                   Chief Executive Officer


(SEAL)

Attest: /s/William G. Green
       --------------------------------
           William G. Green, Secretary