UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 5, 2005

Chiron Corporation

(Exact name of registrant as specified in its charter)

Delaware	0-12798	94-2754624
(State or other	(Commission	(IRS Employer
jurisdiction of	File Number)	Identification No.)
incorporation)

4560 Horton Street, Emeryville, CA		94608
(Address of principal executive offices)		(Zip Code)

Registrant’s telephone number, including area code (510) 655-8730

N/A

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

o Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 8.01 Other Events.

On September 5, 2005, Chiron Corporation (“Chiron”) issued a press release announcing its response to the offer from Novartis AG to acquire the approximately 58% of Chiron shares that it does not already own for $40.00 per share in cash.

A copy of Chiron’s press release of September 5, 2005 is attached hereto as Exhibit 99.1 and is incorporated by reference in this Item 8.01.

Item 9.01. Financial Statements and Exhibits.

(a) Financial statements of businesses acquired.

Not applicable.

(b) Pro forma financial information.

Not applicable.

(d) Exhibits.

Exhibit Number		Description

99.1		Press Release issued September 5, 2005.

# # #

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	CHIRON CORPORATION
	(Registrant)


Date: September 6, 2005	By:	/s/ Jessica Hoover
		Jessica Hoover
		Vice President, Corporate Business
		Development

CHIRON CORP 8-K