<PAGE>



                                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 RESTATED
CERTIFICATE OF INCORPORATION OF CHIRON CORPORATION FILED IN THIS OFFICE ON THE
SEVENTEENTH DAY OF AUGUST, A.D. 1987, AT 9 O'CLOCK A.M.






                                        /s/ Michael Harkins
[SEAL]                                  -----------------------------------
                                        Michael Harkins, Secretary of State

                                        AUTHENTICATION: 1365957
     877229043                               DATE: 08/18/1987

<PAGE>

           RESTATED CERTIFICATE OF INCORPORATION OF CHIRON CORPORATION

          Chiron Corporation, a corporation organized and existing under the
laws of the State of Delaware, hereby certifies as follows:

          1.   Previously this corporation was called Chiron Delaware
Corporation. The original certificate of incorporation was filed on November 21,
1986. The name was changed by amendment to Chiron Corporation on December 24,
1986.

          2.   This Restated Certificate of Incorporation ("Certificate") was
duly adopted by the Board of Directors of the Corporation on June 11, 1987 and
approved by the stockholders of the Corporation at the
Corporation's Annual Meeting of Stockholders on August 12, 1987 in accordance
with the provisions of Sections 242 and 245 of the General Corporation Law of
the State of Delaware. The text of the Certificate of Incorporation as amended
and restated shall be read in full as follows:

          FIRST:    The name of this corporation is: CHIRON CORPORATION.

          SECOND:   The address of the registered office of the corporation in
the State of Delaware is 1209 Orange Street, the City of Wilmington, County of
New Castle, and the name of its registered agent at that address is The
Corporation Trust Company.

          THIRD:    The name and mailing address of the incorporator of the
corporation is:
                    William G. Green
                    Chiron Corporation
                    c/o Brobeck, Phleger & Harrison
                    One Market Plaza, Spear Street Tower
                    San Francisco, CA 94105

          FOURTH:   The purpose of this corporation is to engage in any lawful
act or activity for which corporations may be organized under the General
Corporation Law of Delaware.

          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 thirty-
five million (35,000,000). Five million (5,000,000) shares shall be Preferred
Stock and thirty million (30,000,000) 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

                                       1.

<PAGE>

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 on 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 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 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.

          2.   COMMON STOCK.

          The common stock may be issued from time to time in one or more
series. Twenty-nine million five hundred thousand (29,500,000) 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 shares 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:

                                       2.

<PAGE>

                    (i)    CONVERSION RIGHTS.     The Restricted Common Stock
          may be convertible into or exchangeable for Common Stock, at a
          conversion or 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 the 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 amount per share paid in liquidation on each share of
          the 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 therefor.

          SIXTH:    A Director of this corporation shall not be personally
liable to this corporation or its stockholders for monetary damages for breach
of fiduciary duty as a Director, except for liability (i) for any breach of the
Director's duty of loyalty to this corporation or its stockholders, (ii) for
acts or omissions not in good faith or which involve intentional misconduct or a
knowing violation of law, (iii) under Section 174 of

                                       3.

<PAGE>

the Delaware General Corporation Law, or (iv) for any transaction from which the
Director derived any improper personal benefit. The foregoing sentence
notwithstanding, if the Delaware General Corporation Law hereafter is amended to
authorize further limitations of the liability of a director of a corporation,
then a Director of this corporation, in addition to the circumstances in which a
Director is not personally liable as set forth in the preceding sentence, shall
not be liable to the fullest extent permitted by the Delaware General
Corporation Law as so amended. Any repeal or modification of the foregoing
provisions of this Article SIXTH by the stockholders of this corporation shall
not adversely affect any right or protection of a Director of this corporation
existing at the time of such repeal or modification.

          SEVENTH:

          1.   The number of directors which shall constitute the whole Board of
Directors of this corporation shall be as specified in the Bylaws of this
corporation, subject to the provisions of Article NINTH hereof and this Article
SEVENTH.

          2.   The Board of Directors shall be and is divided into three
classes: Class I, Class II and Class III, which shall be as nearly equal in
number as possible. Each director shall serve for a term ending on the date of
the third annual meeting of stockholders following the annual meeting at which
the director was elected; provided, however, that each initial director in Class
I shall hold office until the annual meeting of stockholders in 1988, each
initial director in Class II shall hold office until the annual meeting of
stockholders in 1989, and each initial director in Class III shall hold
office until the annual meeting of stockholders in 1990. Notwithstanding the
foregoing provisions of this Article SEVENTH, each director shall serve until
his or her successor is duly elected and qualified or until his or her death,
resignation or removal.

          3.   In the event of any increase or decrease in the authorized number
of directors, (i) each director then serving as such shall nevertheless continue
as a director of the class of which he or she is a member until the expiration
of his or her current term, or his or her earlier resignation, removal from
office or death, and (ii) the newly created or eliminated directorship resulting
from such increase or decrease shall be apportioned by the Board of Directors
among the three classes of directors so as to maintain such classes as nearly
equal as possible.

          EIGHTH:   Except as provided by applicable law, the Board of Directors
shall have the exclusive power and authority to fill any vacancies or any newly
created directorships on the Board of Directors upon a vote of two-thirds (2/3)
of the remaining or existing members of the Board of Directors; the stockholders
shall have no right to fill such vacancies. A director appointed by the Board of
Directors to fill a vacancy shall serve for the remainder of the term of the
vacated directorship he or she is filling.

          NINTH:    In furtherance and not in limitation of the powers conferred
by statute, the Board of Directors is expressly authorized to make, repeal,
alter, amend and rescind from time to time any or all of the Bylaws of this
corporation; provided, however, any Bylaw amendment adopted by the Board of
Directors increasing or reducing the authorized number of directors shall
require a resolution adopted by the affirmative vote of not less than seventy-
five percent of the directors.

                                       4.

<PAGE>

          TENTH:    No action shall be taken by the stockholders except at an
annual or special meeting of stockholders. No action shall be taken by
stockholders by written consent.

          ELEVENTH:

          1.   The affirmative vote of the holders of not less than sixty-six
and two-thirds percent (66-2/3%) of the outstanding shares of "Voting Stock" (as
hereinafter defined) shall be required for the approval or authorization of any
"Business Combination" (as hereinafter defined) of this corporation or any
Subsidiary of this corporation with any "Related Person" (as hereinafter
defined), notwithstanding the fact that no vote may be required, or that a
lesser percentage may be specified by applicable law, in any agreement with any
national securities exchange or otherwise; provided, however, that:

               (a)  the Voting Stock of which the Related Person is the
beneficial owner (as hereinafter defined) shall not be included in the
denominator or the numerator in calculating the sixty-six and two-thirds percent
(66-2/3%) of the outstanding shares of Voting Stock required to approve or
authorize the Business Combination unless all of the following conditions are
met:

                    (i)     The Business Combination shall include the
          acquisition of all of the outstanding stock of this corporation of
          which the Related Person otherwise involved is not the Beneficial
          Owner and the consideration to be received per share by holders of a
          particular class or series of capital stock, as the case may be, of
          this corporation in the Business Combination is not less than the
          highest of:
                            (A)    the highest per share price (including
                    brokerage commissions, transfer taxes and soliciting
                    dealers' fees) paid by or on behalf of such Related Person
                    in acquiring beneficial ownership of any of its holdings of
                    such class or series of capital stock of this corporation
                    (i) within the two-year period immediately prior to the date
                    of the consummation of the Business Combination (the
                    "Combination Date") or (ii) in the transaction or series of
                    transactions in which such Related Person became a Related
                    Person, whichever is higher; or

                            (B)    the Fair Market Value per share of the shares
                    of capital stock being acquired in the Business Combination
                    as of the Combination Date; or

                            (C)    in the case of Common Stock, the per share
                    book value of the Common Stock as reported at the end of the
                    fiscal quarter immediately prior to the Combination Date,
                    and in the case of Preferred Stock, the highest preferential
                    amount per share to which the holders of shares of such
                    class or series of Preferred Stock would be entitled in the
                    event of any voluntary or involuntary liquidation,
                    dissolution or winding up of the affairs of this
                    corporation, regardless of whether the Business Combination
                    to be consummated constitutes such an event.

                                       5.

<PAGE>

                            The provisions of this paragraph 1(a)(i) shall be
          required to be met with respect to every class or series of
          outstanding capital stock, whether or not such Related Person has
          previously acquired any shares of a particular class or series of
          capital stock and whether or not any shares of a particular class or
          series or of any class or series otherwise are involved in the
          Business Combination. In all above instances, appropriate adjustments
          shall be made for recapitalization and for stock dividends, stock
          splits and like distributions;

                    (ii)    A proxy or information statement describing the
          proposed Business Combination and complying with the requirements of
          the Securities Exchange Act of 1934, as amended, and the general rules
          and regulations thereunder (or any subsequent provisions replacing
          such Act, rules or regulations) shall be mailed by such Related Person
          to the stockholders of the Company at least 30 days prior to the
          Consummation Date (whether or not such proxy or information statement
          is required to be mailed pursuant to such Act or subsequent provisions
          thereof); and

                    (iii)   The consideration to be received by holders of a
          particular class or series of capital stock shall be in cash;

and provided further that:

               (b)  The voting requirements set forth above shall not be
applicable and such Business Combination shall require only such affirmative
vote, if any, as is required by applicable law, any agreement with any national
securities exchange, or otherwise, if the "Continuing Directors" (as hereinafter
defined) of this corporation by at least a two-thirds (2/3) vote have expressly
approved such Business Combination either in advance of or subsequent to such
Related Person becoming a Related Person (it being understood that this
condition shall not be capable of satisfaction unless there is at least one
Continuing Director).

          2.   For purposes of this Article ELEVENTH:

               (a)  The term "Business Combination" shall mean any (i) merger or
consolidation of this corporation or a Subsidiary with a Related Person or any
other corporation which is, or after such merger or consolidation would be, an
"Affiliate" or "Associate" (as hereinafter defined) of a Related Person, (ii)
sale, lease, exchange, mortgage, pledge, transfer or other disposition (in one
transaction or a series of transactions) of all or any "Substantial Part" (as
hereinafter defined) of the assets of this corporation or of a Subsidiary to a
Related Person, (iii) adoption of any plan or proposal for the liquidation or
dissolution of this corporation proposed by or on behalf of a Related Person,
(iv) sale, lease, exchange or other disposition, including without limitation a
mortgage or other security device, of all or any Substantial Part of the assets
of a Related Person to this corporation or a Subsidiary, (v) issuance or pledge
of securities of this corporation or a Subsidiary to or with Related Person,
(vi) reclassification of securities (including any reverse stock split) or
recapitalization of this corporation or any other transaction that would have
the effect, either directly or indirectly, of increasing the proportionate share
of any class of equity or convertible securities of this corporation or any
Subsidiary which is directly or indirectly beneficially owned by any Related
Person, and (vii) agreement, contract or other arrangement providing for any of
the transactions described in this definition of Business Combination.

                                       6.

<PAGE>

               (b)  The term "person" shall mean any individual, firm,
corporation or other entity and shall include any group comprised of any person
and any other person with whom such person or any Affiliate or Associate of such
person has any agreement, arrangement, or understanding, directly or indirectly,
for the purpose of acquiring, holding, voting or disposing of Voting Stock of
this corporation (other than proxies acquired pursuant to a solicitation under
Regulation 14 of the Securities and Exchange Commission).

               (c)  The term "Related Person" shall mean any person (other than
this corporation or a Subsidiary, or any person who shall have been a director
of this corporation on January 1, 1987, and other than any profit-sharing,
employee stock ownership or other employee benefit plan of this corporation, or
any Subsidiary or any trustee of or fiduciary with respect to any such plan when
acting in such capacity) who or which:

                    (i)     is the beneficial owner (as hereinafter defined) of
          ten percent (10%) or more of the Voting Stock;

                    (ii)    is an Affiliate or Associate of any Related Person
          other than an Affiliate or Associate of such Related Person solely by
          reason of being an Affiliate or Associate of this corporation or one
          of its Subsidiaries; or

                    (iii)   is an assignee of or has otherwise succeeded to the
          beneficial ownership of any shares of Voting Stock which were at any
          time within the two-year period immediately prior to the date in
          question beneficially owned by any Related Person, if such assignment
          or succession shall have occurred in the course of a transaction or
          series of transactions not involving a public offering within the
          meaning of the Securities Act of 1933, as amended.

               (d)  A person shall be a "beneficial owner" of any Voting Stock:

                    (i)     which such person or any of its Affiliates or
          Associates beneficially owns directly or indirectly;

                    (ii)    which such person or any of its Affiliates or
          Associates has, directly or indirectly, (A) the right to acquire
          (whether such right is exercisable immediately or only after the
          passage of time), pursuant to any agreement, arrangement or
          understanding or upon the exercise of conversion rights, exchange
          rights, warrants or options, or otherwise, or (B) the right to vote
          pursuant to any agreement, arrangement, or understanding (other than
          proxies acquired pursuant to a proxy solicitation under Regulation 14
          of the Securities and Exchange Commission); or

                    (iii)   which are beneficially owned, directly or
          indirectly, by any other person with which such person or any of its
          Affiliates or Associates has any agreement, arrangement or
          understanding (other than proxies acquired  pursuant to a proxy
          solicitation under Regulation 14 of the Securities and Exchange
          Commission).

                                       7.

<PAGE>

               (e)  For the purposes of determining whether a person is a
Related Person pursuant to subparagraph (c) of this paragraph 2, the number of
shares of Voting Stock deemed to be outstanding shall include shares deemed
owned through application of subparagraph (d) of this paragraph 2 but shall not
include any other shares of Voting Stock which may be issuable pursuant to any
agreement, arrangement or understanding, or upon exercise of conversion rights,
warrants or options, or otherwise.

               (f)  The terms "Affiliate" or "Associate" shall have the
respective meanings ascribed to such terms in Rule 12b-2 of the General Rules
and Regulations under the Securities Exchange Act of 1934, as in effect on
January 1, 1987.

               (g)  The term "Subsidiary" means any corporation of which a
majority of any class of equity security is owned, directly or indirectly, by
this corporation; provided, however, that for the purposes of the definition of
Related Person set forth in subparagraph (c) of this paragraph 2, the term
"Subsidiary" shall mean only a corporation of which a majority of each class of
equity security is owned, directly or indirectly, by this corporation.

               (h)  The term "Continuing Director" means:

                            (i)    any member of the Board of Directors, while
          such person is a member of the Board of Directors, who was member of
          the Board of Directors on January 1, 1987, or who (a) is not a Related
          Person, or a representative of any Related Person, who has been a
          Related Person for less than the immediately preceding twenty-four
          months, and (b) was a member of the Board of Directors prior to the
          time that any Related Person, who has been a Related Person for less
          than the immediately preceding twenty-four months, became a Related
          Person, and

                            (ii)   any successor of a Continuing Director, while
          such successor is a member of the Board of Directors, who (a) is not a
          Related Person, or a representative of a Related Person and (b) was
          recommended or elected to succeed a Continuing Director by a majority
          of Continuing Directors.

               (i)  The term "Substantial Part" shall mean (1) more than twenty
percent (20%) of the fair market value, as determined by a majority of the
Continuing Directors, of the total consolidated assets of this corporation and
its Subsidiaries taken as a whole as of the end of its most recent fiscal year
ended prior to the time the determination is being made, and (2) such other
assets as shall be deemed by two-thirds (2/3) of the Continuing Directors to
constitute a substantial part of the assets of this corporation.

               (j)  The term "Unaffiliated Stockholders" shall mean all persons
holding shares of the Corporation entitled to vote on a Business Combination
other than a Related Person.

               (k)  The term "Voting Stock" shall mean all of the outstanding
shares of Common Stock and the outstanding shares of Preferred Stock entitled to
vote for the election of directors, and each reference to a proportion of shares
of Voting Stock shall refer to such proportion of the votes entitled to be cast
by such shares voting as one class.

                                       8.

<PAGE>

               (l)  The term "Fair Market Value" means, in the case of stock,
the highest closing sale price during the thirty-day period immediately
preceding the date in question of a share of such stock on the principal United
States securities exchange registered under the Securities Exchange Act of 1934
on which such stock is listed, or on the National Association of Securities
Dealers, Inc. Automated Quotations System or any successor system then in use,
or if no such quotations are available, the fair market value on the date in
question of a share of such stock as determined in good faith by a majority of
the Continuing Directors.

               (m)  A Related Person shall be deemed to have acquired a share of
the Voting Stock of this corporation at the time when such Related Person became
the beneficial owner thereof. If a majority of the Continuing Directors is not
able to determine the price at which a Related Person has acquired a share of
Voting Stock of this corporation, such price shall be deemed to be the Fair
Market Value of the shares in question at the time when the Related Person
became the beneficial owner thereof. With respect to shares owned by Affiliates,
Associates or other persons whose ownership is attributed to a Related Person
under the foregoing definition of a Related Person, the price deemed to be paid
therefor by such Related Person shall be the price paid upon the acquisition
thereof by such Affiliate, Associate or other person, or, if such price is not
determinable by a majority of the Continuing Directors, the Fair Market Value of
the shares in question at the time when the Affiliate, Associate or other such
person became the beneficial owner thereof.

          3.   (a)  Notwithstanding any other provision of this Restated
Certificate of Incorporation, the provisions of this Article ELEVENTH may not be
repealed, altered or amended in any respect, and no provision to this Restated
Certificate of Incorporation may be adopted that is inconsistent with the terms
of this Article ELEVENTH, unless such repeal, alteration, amendment or adoption
is approved by the affirmative vote of the holders of not less than sixty-six
and two-thirds percent (66-2/3%) of the Voting Stock of this corporation other
than Voting Stock beneficially owned by Related Persons, unless such action is
declared advisable by the affirmative vote of not less than two-thirds (2/3) of
both (a) the entire Board of Directors and (b) the Continuing Directors, in
which event the stockholder vote required for any such approval shall be as now
or hereafter prescribed by the provisions of the General Corporation Law of
Delaware.

               (b)  The fact that any Business Combination complies with the
provisions of paragraph 1(b) of this Article ELEVENTH shall not be construed to
impose any fiduciary duty, obligation or responsibility on the Board of
Directors, or any member thereof, to approve such Business Combination or
recommend its adoption or approval to the stockholders of this corporation, nor
shall such compliance limit, prohibit or otherwise restrict in any manner the
Board of Directors, or any member thereof, with respect to evaluations of or
actions and responses taken with respect to such Business Combination.

          TWELFTH:  This corporation reserves the right to amend, alter, change
or repeal any provision contained in this Restated Certificate of Incorporation,
in the manner now or hereafter prescribed by statute, and all rights conferred
on stockholders herein are granted subject to this reservation. Notwithstanding
the foregoing, the provisions set forth in Article SEVENTH, Article EIGHTH,
Article NINTH, Article TENTH and this Article TWELFTH may not be repealed or
amended in any respect unless such repeal or amendment is approved by the
affirmative vote of not less than sixty-six and two-

                                      9

<PAGE>

thirds percent (66-2/3%) of the total voting power of all outstanding shares
of stock in this corporation entitled to vote thereon, unless such action is
declared advisable by the affirmative vote of not less than two-thirds (2/3)
of the entire Board of Directors, in which event the stockholder vote
required for any such approval shall be as now or hereafter prescribed by the
provisions of the General Corporation Law of Delaware.

          THIRTEENTH:   This corporation reserves the right to amend, alter,
change or repeal any provision contained in this Restated Certificate of
Incorporation, in the manner now or hereafter prescribed by statute, and all
rights conferred on stockholders herein are granted subject to this reservation.



                                       10.

<PAGE>

                    AMENDMENT OF CERTIFICATE OF INCORPORATION

          Subject to the provision of Section 242 of the General Corporation Law
of the State of Delaware, the Corporation reserves the right to amend, alter,
change, or repeal any provision contained in this Certificate in the manner now
or hereafter prescribed by statute, and all rights conferred upon stockholders
herein are granted subject to this reservation.

          IN WITNESS WHEREOF, said CHIRON CORPORATION has caused its corporate
seal to be hereunto affixed and this Certificate to be signed by EDWARD E.
PENHOET, its President and Chief Executive Officer, and attested by WILLIAM G.
GREEN, its Secretary, this 13th day of August, 1987.

                               CHIRON CORPORATION



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



[SEAL]

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