FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * Leader Meghan   2. Issuer Name and Ticker or Trading Symbol CHIRON CORP [CHIR] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) V.P., Bus. Sup. Svcs. & CIO (Last) (First) (Middle) 4560 HORTON STREET 3. Date of Earliest Transaction (Month/Day/Year) 03/19/2006 (Street) EMERYVILLE, CA 94608 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 03/19/2006   F   269 (1) D $ 45.78 5,716 (2) D   Common Stock               1,432 I Held by a Trust

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Leader Meghan 4560 HORTON STREET EMERYVILLE, CA 94608			V.P., Bus. Sup. Svcs. & CIO

Signatures

Meghan Leader by Naima Robinson as Atty-in-Fact		03/21/2006
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	These shares were withheld by the Issuer in satisfaction of the required withholdings taxes in a transaction exempt under Rule 16b-3(e).
(2)	Includes share rights covering 1,950 shares of the Issuer's common stock previously awarded to the Reporting Person in an exempt transaction under SEC Rule 16b-3(d). The rights will vest, and the underlying shares of the Issuer's common stock will become issuable, as to (i) 40% of the total number of shares upon the Reporting Person's completion of two years of service with the Issuer measured from the award date and (ii) the remaining shares upon the Reporting Person's completion of four years of service with the Issuer measured from the award date, subject in each instance to adjustment to reflect any leave of absence taken by the Reporting Person. However, all the shares subject to the award will vest and become issuable on an accelerated basis upon the Issuer's termination of the Reporting Person's service without cause.

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