Chiron Grants Nonexclusive HCV License to Boehringer Ingelheim

December 18, 2003

EMERYVILLE, Calif., Dec. 18 /PRNewswire-FirstCall/ -- Chiron Corporation

(Nasdaq: CHIR) today announced that it has granted to Boehringer Ingelheim

International GmbH a nonexclusive license for the research, development and

commercialization of small molecule therapeutics against hepatitis C virus

(HCV) drug targets. Under the terms of the agreement, Boehringer Ingelheim

would pay Chiron up-front license fees, milestone payments and royalties on

products. The specific financial terms and other details of the license were

not disclosed.

" This agreement is a further example of Chiron's strong commitment to

making its technology widely available to companies working to find

therapies

for hepatitis C, " said G. Green, Esq., Chiron general counsel. " We

continue to strategically leverage our HCV intellectual property and

actively

license this technology to other companies, while we pursue our own research

into therapeutic agents for hepatitis C. "

About Hepatitis C

In 1987, Chiron scientists Houghton, Ph.D.; Qui-Lim Choo, Ph.D.;

and Kuo, Ph.D., cloned and first identified HCV as the cause of

transfusion-related non-A, non-B hepatitis. This breakthrough marked the

first

time a virus was cloned before it had been grown in tissue culture or

otherwise isolated. The Chiron scientists received the prestigious Lasker

Award in recognition of this discovery. Since the initial work, Chiron has

been granted more than 100 HCV-related patents in over 20 countries,

including

patents directed to hepatitis C polypeptides encoded throughout the genomes

of

HCV. Such polypeptides can be used in a variety of medical applications,

including blood screening, clinical diagnosis, vaccines and as therapeutic

targets for drug screening. A number of therapeutic companies have been

granted nonexclusive licenses to Chiron's HCV technology for drug screening

purposes, including Bristol-Myers Squibb, GlaxoKline, Japan Tobacco

Inc.,

Gilead and Pfizer.

About Chiron

Chiron Corporation, headquartered in Emeryville, California, is a global

pharmaceutical company that leverages a diverse business model to develop

and

commercialize high-value products that make a difference in people's lives.

The company has a strategic focus on cancer and infectious disease. Chiron

applies its advanced understanding of the biology of cancer and infectious

disease to develop products from its platforms in proteins, small molecules

and vaccines. The company commercializes its products through three business

units: BioPharmaceuticals, Vaccines and Blood Testing. For more information

about Chiron, visit the company's website at http://www.chiron.com.

This news release contains forward-looking statements regarding royalty

revenue and the possible grant of additional licenses that involve risks and

uncertainties and are subject to change. A full discussion of the company's

operations and financial condition, including factors that may affect its

business and future prospects, is contained in documents the company has

filed

with the SEC, including the form 10-Q for the quarter ended September 30,

2003, and the form 10-K for the year ended December 31, 2002, and will be

contained in all subsequent periodic filings made with the SEC.

Consistent with SEC Regulation FD, we do not undertake an obligation to

update the forward-looking information we are giving today.

SOURCE Chiron Corporation

Web Site: http://www.chiron.com

December 18, 2003