Chiron Confirms Proposed Purchase of BETASERON Assets by Schering AG Under Change-in-Control Option

Chiron Corporation (Nasdaq:CHIR) today announced that
Schering AG has provided formal notice to Chiron of its intention to
exercise its option under its collaboration agreement with Chiron to
purchase or lease all assets used by Chiron in the manufacture for
Schering of BETASERON(R) interferon beta-1b products and all
contractual rights at their fair market or lease value. The
purchase/lease option, as stipulated in a change-in-control clause in
the agreement, is subject to the closing of the proposed acquisition
of Chiron by Novartis AG. The agreement requires that the value be
determined by an independent third party mutually agreed upon by both
parties. The collaboration agreement between Chiron and Schering is
set to expire in October 2008.

   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, including
statements regarding the sale or lease of assets to Schering and the
proposed acquisition of Chiron by Novartis AG, that involve risks and
uncertainties and are subject to change. Forward-looking statements
often address our expected future performance and often contain words
such as "expects," "anticipates," "intends," "plans," "believes,"
"seeks" or "will." 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
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 September
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, including, among others, regulatory review and
approvals, manufacturing capabilities, intellectual property
protections and defenses, litigation, and marketing effectiveness. No
assurance can be given as to whether or not Schering will purchase or
lease the assets described in this press release or that the
transactions contemplated by the merger agreement with Novartis AG
will be consummated. 
   Chiron does not undertake an obligation to update the
forward-looking information the company is giving today.

   NOTE: BETASERON is a trademark of Schering AG.