Exhibit 10.504

PERSONAL AND CONFIDENTIAL

                        , 2002

«First_Name» «Last_Name»
«JOB_TITLE»
Chiron Corporation
«ADDRESS», M/S «MS»
«CITY_STATE_ZIP»

        Re:    Restricted Share Right Grant

Dear: «First_Name»

        Pursuant to the Chiron Corporation 1991 Stock Option Plan (the "Plan"),
Chiron Corporation (the "Company") hereby grants you «Shrs            Grntd»
(«Shrs            Grntd            Wrds») restricted share rights ("share
rights") with respect to its Common Stock ("Common Stock"). These share rights
are granted to you in accordance with the restrictions, terms, and conditions
hereinafter set forth and are in all respects limited and conditioned by the
provisions of the Plan.

        1.    Each share right entitles you to receive one share of Common Stock
on the Payment Date applicable to such share right if you remain employed with
the Company through that date. The Payment Date for forty percent (40%) of your
share rights will be August 31, 2003; the Payment Date for the remaining sixty
percent (60%) of your share rights will be August 31, 2005. A certificate
representing the share of stock payable under a share right will be issued
without restriction on the Payment Date provided that your share rights have not
been terminated or canceled before such date in accordance with the following
provisions.

        2.    If you voluntarily terminate employment with the Company for any
reason other than death or permanent disability or if the Company terminates
your employment for Cause before the Payment Date of a share right, subject to
paragraph 8 below, each share right you hold will be canceled automatically and
no shares of Common Stock will be issued thereunder.

        3.    If you terminate employment by reason of death or permanent
disability or if the Company terminates your employment for any reason other
than for Cause before August 31, 2005, all share rights then held by you will be
canceled automatically except as follows:

        (i)    if your termination date is after August 31, 2002 and before
August 31, 2003, you will be issued, as soon as practicable following such
termination of employment, that number of shares of Common Stock equal to the
total number of your share rights with an August 31, 2003 Payment Date
multiplied by a fraction, the numerator of which is the number of whole months
of your employment after August 31, 2001 and the denominator of which is
twenty-four (24), or

        (ii)  if your termination date is after August 31, 2003, and before
August 31, 2005, you will be issued, as soon as practicable following such
termination of employment, that number of shares of Common Stock equal to the
total number of your share rights with an August 31, 2005 Payment Date
multiplied by a fraction, the numerator of which is the number of whole months
of your employment after August 31, 2003 and the denominator of which is
twenty-four (24).

You will be deemed to be permanently disabled if, by reason of any medically
determinable physical or mental impairment expected to result in death or to be
of continuous duration of not less than 12 months, you are unable to engage in
any substantial gainful employment.

        4.    The issuance of shares under a share right is subject to all
applicable tax withholding obligations. In order to satisfy such tax withholding
obligations, the number of shares of Common

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Stock which would otherwise be paid to you on any date will be reduced by that
number of shares which, as of that date, has an aggregate Fair Market Value (as
defined in the Plan) equal to the total amount of tax withholding obligations
applicable to the shares otherwise payable on that date.

        5.    Your share rights hereunder may not be sold, assigned,
transferred, alienated, subject to garnishment or otherwise encumbered in any
manner other than by transfer, to the extent provided below, by Will or the laws
of descent and distribution. In the event of your death prior to the issuance of
shares of Common Stock under your share rights, any shares issuable thereunder
by reason of your death will pass pursuant to your Will or by the laws of
descent and distribution.

        6.    The issuance of shares of Common Stock hereunder shall be subject
to compliance by the Company and yourself or your beneficiary with all
applicable requirements of law relating thereto and with all regulations of any
stock exchange on which the Common Stock may be listed at the time of such
issuance.

        7.    If the Company or its stockholders enter into an agreement to
dispose of all or substantially all of the assets of the Company, enter into an
agreement to merge or consolidate with another entity, or enter into a plan of
reorganization or liquidation, while your restricted share rights are
outstanding, then each outstanding share right will become vested and paid in
full, immediately before the consummation of such transaction. However, no
acceleration of the vesting or payment date will occur if the agreement requires
as a prerequisite to the consummation of any such transaction that each such
outstanding share right will be either assumed by the successor corporation or
parent thereof or be replaced with a comparable share right in the successor
corporation or parent thereof.

        8.    If there is a Change in Control of the Company pursuant to which
the share rights continue and within twenty-four (24) calendar months thereafter
there is a Qualifying Termination of your employment, then the share rights
which remain outstanding at the time of such Qualifying Termination will vest
and will be paid out in full.

        9.    For this letter agreement, the following definitions apply:

        a.    "Change in Control" of the Company shall be deemed to have
occurred as of the first day that any one or more of the following conditions is
satisfied and regulatory approval has been granted if necessary:

        (i)    The "beneficial ownership" (as defined in Rule 13d-3 under the
Securities Exchange Act of 1934) of securities representing more than thirty
percent (30%) of the combined voting power of all securities of the Company is
acquired, directly or indirectly, by a Person (other than the Company, any
trustee or other fiduciary holding securities under an employee benefit plan of
the Company or an affiliate thereof, or any corporation owned, directly or
indirectly, by the stockholders of the Company in substantially the same
proportions as their ownership of stock of the Company); or

        (ii)  During any period of two (2) consecutive years, individuals who at
the beginning of such period constitute the Board of Directors of the Company
and any new director (other than a director designated by a person who has
entered into an agreement with the Company to effect a transaction described in
i. above) whose election by the Board of Directors or nomination for election by
the Company's stockholders was approved by a vote of at least two-thirds of the
directors then still in office who either were directors at the beginning of the
period or whose election or nomination for election was previously so approved,
cease for any reason to constitute a majority thereof; or

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        (iii)  The stockholders of the Company approve a definitive agreement to
sell or otherwise dispose of all or substantially all of its assets, or adopt a
plan for liquidation, provided that such sale or liquidation has not been
abandoned.

Notwithstanding anything else contained herein to the contrary, in no event
shall a Change in Control be deemed to have occurred by reason of a purchase, or
series of purchases of Company stock by Novartis or its successor such that the
acquiring entity remains subject to the terms of that certain Governance
Agreement dated as of January 5, 1995, as amended through December 9, 2000,
provided the acquiring entity's Company stock holdings, direct or indirect, in
the aggregate, represent less than seventy-nine and nine-tenths of a percent
(79.9%) of the combined voting power of all outstanding Company securities. In
addition, in no event shall a Change in Control be deemed to have occurred, with
respect to you, if you are part of a purchasing group that consummates the
Change-in-Control transaction. You shall be deemed "part of a purchasing group"
for purposes of the preceding sentence if you are an equity participant in the
purchasing company or group (except for: (i) passive ownership of less than
three percent (3%) of the stock or other equity of the purchasing company; or
(ii) ownership of equity participation in the purchasing company or group which
is otherwise not significant, as determined prior to the Change in Control by a
majority of the nonemployee continuing Directors).

        b.    "Qualifying Termination" means: (i) an involuntary termination of
your employment by the Company for reasons other than death, permanent
disability, as defined in paragraph 3, above, or Cause, or (ii) a voluntary
termination by you for Good Reason pursuant to a written notice of termination
delivered to the Company; provided that, if upon receiving such notice of
termination, the Company requests that you remain an employee for a period
ending no later than six (6) months following the date of the Change in Control
(the "Transition Employment Period") with compensation and benefits equal to or
greater than your compensation and benefits immediately before the Qualifying
Termination (or, if more favorable to you, immediately before the Change in
Control), you will not be deemed to have a Qualifying Termination unless you
remain employed throughout the Transition Period or your employment earlier
terminates due to death, disability or involuntary termination by the
Corporation for reason other than Cause.

        c.    "Cause" means: (i) your willful failure to substantially perform
your duties with the Company (other than any such failure resulting from
permanent disability or occurring after you have notified the Company in writing
of your termination for Good Reason, but, in the latter case, only if the
Company has not requested a Transition Employment Period for you), (ii) your
material act of dishonesty, fraud or embezzlement against the Company,
unauthorized disclosure of confidential information or trade secrets of any of
the Company or an affiliate (whether or not in violation of any confidentiality
agreement) or other willful conduct that is demonstrably injurious to the
Company, monetarily or otherwise; or (iii) your having been convicted of a
felony. No act, or failure to act, on your part will be deemed "willful" unless
done, or omitted to be done, by you not in good faith and without reasonable
belief that the action or omission was in the best interests of the Company.

        d.    "Good Reason" shall mean, without your express written consent,
the occurrence of any one or more of the following:

        (i)    The assignment of you to duties materially inconsistent with your
authorities, duties, responsibilities as an employee of the Company, or a
material reduction in the nature or status of your authorities, duties, or
responsibilities from those in effect immediately preceding the Change in
Control;

        (ii)  The Company's requiring you to be based at a location which is at
least fifty (50) miles further from your current primary residence than is such
residence from the

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Company's current headquarters, except for required travel on the Company's
business to an extent substantially consistent with your business obligations as
of the Effective Date;

        (iii)  A material reduction in your Base Salary or bonus opportunity as
in effect on the Effective Date of the Change in Control or as the same shall be
increased from time to time;

        (iv)  A material reduction in your level of participation in any of the
Company's short- and/or long-term incentive compensation plans, or employee
benefit or retirement plans, policies, practices, or arrangements in which you
participate in immediately preceding the Change in Control; provided, however,
that reductions in the levels of participation in any such plans shall not be
deemed to be "Good Reason" if your reduced level of participation in each such
program remains substantially consistent with the average level of participation
of other employees who have positions commensurate with your position. Long-term
incentive plans shall mean the Chiron Executive Long-Term Incentive Plan, the
1991 Stock Option Plan, and any other similar plans instituted by the Company.

However, the occurrence of an event set forth in (i) through (iv) above shall
not constitute Good Reason if the Company has cured such event within fifteen
(15) days of receipt of written notice from you that such event has occurred and
constitutes Good Reason.

        10.  Neither you nor, in the event of your death, your beneficiary shall
have any rights as a shareholder with respect to the shares of Common Stock
issuable hereunder until you shall have been issued a stock certificate for such
shares. It is the intention of the parties that the Company's obligations under
your share rights are unfunded for purposes of the Internal Revenue Code and
that the Employee Retirement Income Security Act of 1974 does not apply to your
share rights.

        11.  The Compensation Committee, may, in its discretion, modify or waive
any or all of the terms, conditions or restrictions hereof, provided, however,
that no such modification or waiver may, without your or, if applicable, your
beneficiary's, consent, adversely affect the rights of you or your beneficiary
hereunder.

        12.  The Compensation Committee has full authority to administer the
Plan, including authority to interpret and construe any provision thereof and
hereof and to adopt such rules and regulations for administering the Plan as it
may deem necessary. Decisions of the Compensation Committee are final and
binding on all persons who have an interest in the Plan.

        13.  This grant shall not constitute a contract of employment. The
Company (or any subsidiary employing you) may terminate or change the terms of
your employment at any time and for any reason and whether or not such
termination or change causes a loss of rights under the Plan, except to the
extent that the terms of any employment contract or, with respect to changes in
your compensation, any written compensation agreement between the Company and
you may expressly provide otherwise.

    Very truly yours,     CHIRON CORPORATION          
 
 
By:
 

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Seán P. Lance
Chairman and
Chief Executive Officer

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