Ownership Submission
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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(Print or Type Responses)
1. Name and Address of Reporting Person *
BRYSON VAUGHN D
  2. Issuer Name and Ticker or Trading Symbol
CHIRON CORP [CHIR]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director _____ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
4560 HORTON STREET
3. Date of Earliest Transaction (Month/Day/Year)
04/19/2006
(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 04/19/2006   D(1)   12,093 (2) D $ 48 0 D  

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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
Stock Option (Right to Buy) $ 20.5938 04/19/2006   D(3)     5,179   (4) 04/19/2006 Common Stock 5,179 $ 27.4062 (3) 0 D  
Stock Option (Right to Buy) $ 16.1563 04/19/2006   D(3)     5,246   (4) 04/19/2006 Common Stock 5,246 $ 31.8437 (3) 0 D  
Stock Option (Right to Buy) $ 21.3125 04/19/2006   D(3)     5,102   (4) 04/19/2006 Common Stock 5,102 $ 26.6875 (3) 0 D  
Stock Option (Right to Buy) $ 35.8075 04/19/2006   D(3)     15,000   (4) 04/19/2006 Common Stock 15,000 $ 12.1925 (3) 0 D  
Share Rights Award (5) 04/19/2006   A(6)   3,233     (7) 04/19/2006 Common Stock 3,233 $ 0 3,233 D  
Share Rights Award (5) 04/19/2006   D(8)     3,233   (7) 04/19/2006 Common Stock 3,233 $ 48 (8) 0 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
BRYSON VAUGHN D
4560 HORTON STREET
EMERYVILLE, CA 94608
  X      

Signatures

 Vaughn Bryson, By Naima Robinson as Atty-in-Fact   04/19/2006
**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) The disposition was effected pursuant to the terms of the merger agreement between the Issuer and Novartis AG dated as of October 30, 2005 and as subsequently amended April 3, 2006 (the "Merger Agreement"), and involved the exchange of each share for a cash payment in the amount of $48. The disposition was approved by the Compensation Committee of the Issuer's Board of Directors and is accordingly an exempt transaction pursuant to SEC Rule 16b-3(e).
(2) Includes share right awards covering 11,815 shares of the Issuer's common stock which were also exchanged for a cash payment pursuant to the Merger Agreement.
(3) The option was cancelled pursuant to the terms of the Merger Agreement in exchange for a cash payment per cancelled option share equal to $48 less the exercise price per share in effect for that option. Such disposition of the option was approved by the Compensation Committee of the Issuer's Board of Directors and is accordingly an exempt transaction pursuant to SEC Rule 16b-3(e).
(4) The option was vested and fully exercisable as to all the shares at the time of cancellation.
(5) One-for-One
(6) Represents a share rights award for 3,233 vested shares of the Issuer's common stock made to the Reporting Person in a transaction exempt under SEC Rule 16b-3(d).
(7) The share rights were vested and fully exercisable as to all the shares at the time of cancellation.
(8) The share rights were cancelled pursuant to the terms of the Merger Agreement in exchange for a cash payment equal to $48 per share of the Issuer's common stock underlying the cancelled share rights. Such disposition of the share rights was approved by the Compensation Committee of the Issuer's Board of Directors and is accordingly an exempt transaction pursuant to SEC Rule 16b-3(e).

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