Chiron Responds to Novartis Offer

Chiron Corporation (NASDAQ: CHIR) today issued the
following statement from Chiron's independent board directors in
response to the offer from Novartis AG (NYSE: NVS) on September 1,
2005, to acquire the approximately 58% of Chiron shares that Novartis
does not already own for $40 per Chiron share in cash:
   "Over the 10 years since Novartis has been Chiron's largest
stockholder, Chiron has regularly discussed with Novartis a number of
strategic initiatives, including mergers, significant acquisitions and
other transactions, including transactions initiated by Novartis. As a
result, Chiron has had an on-going dialogue with Novartis regarding
its intentions with respect to its investment in Chiron. Chiron's
independent directors have not, however, solicited an offer to buy
Chiron.
   "We are pleased by the fact that Novartis continues to recognize
Chiron's promising prospects, as do Chiron's independent directors.
   "After thorough analysis and consideration of Novartis' offer to
acquire the shares of Chiron it does not already own for $40.00 per
share in cash, the independent directors of Chiron have determined
that this offer is inadequate."

   About Chiron

   Chiron delivers innovative and valuable products to protect human
health by advancing pioneering science across the landscape of
biotechnology. The company works to deliver on the limitless promise
of science and make a positive difference in people's lives. For more
information about Chiron, please visit www.chiron.com.

   This news release contains forward-looking statements that involve
risks and uncertainties and are subject to change. A discussion of the
company's operations and financial condition, including factors that
may affect its business and future prospects that could cause actual
results and developments to differ materially from those expressed or
implied by any forward-looking statements, is contained in documents
the company has filed with the SEC, including the Form 10-K for the
year ended December 31, 2004, and the Form 10-Q for the quarter ended
June 30, 2005, and will be contained in all subsequent periodic
filings made with the SEC. These documents identify important factors
that could cause the company's actual performance to differ from
current expectations. Chiron does not undertake an obligation to
update the forward-looking information the company is giving today.