Chiron Announces Merger Agreement with Novartis

October 31, 2005

Applied Clinical Trials

Novartis to Acquire Outstanding 58 Percent of Chiron Shares for $45.00 Per Share in Cash

EMERYVILLE, Calif. – Oct 31, 2005 – Chiron Corporation (NASDAQ:CHIR) today announced that it has entered into a definitive merger agreement with Novartis under which Novartis will acquire all of the shares of Chiron that it does not currently own. Novartis will acquire approximately 113 million Chiron shares, or 58 percent of all Chiron shares, for $45.00 per Chiron share, or a total of approximately $5.1 billion, in cash.

"Chiron has recently made tremendous strides, including returning to the U.S. influenza vaccine market, building a compelling oncology pipeline and extending our growth in the Blood Testing business. We can all be rightfully proud of these achievements," said Howard Pien, chief executive officer of Chiron. "Chiron's non-Novartis directors have unanimously determined that this transaction with Novartis is in the best interests of Chiron's shareholders. We believe that Chiron's businesses will have significant growth opportunities as part of Novartis, which will enable us to continue to bring innovative products to patients."

Chiron's global Vaccines business, the fifth largest in the world and one of the largest suppliers of influenza vaccines, provides Novartis with entry into an increasingly attractive segment of the healthcare market and a promising source of growth. Chiron's Blood Testing business adds a high-value profit driver to Novartis and may offer a potential platform for future developments in molecular diagnostics. Chiron's BioPharmaceuticals business, which includes a portfolio of marketed products for cancer and infectious diseases as well as promising oncology research and development programs, will strengthen Novartis' specialty pharmaceutical portfolio and oncology pipeline.

The merger agreement is subject to the approval of the majority of Chiron's shareholders (other than Novartis), U.S. and European regulatory approvals and other customary closing conditions. It is expected to be completed in the first half of 2006.

"Over the course of Chiron's 24-year history as an independent company, the work of Chiron scientists and the products developed, manufactured and marketed by Chiron have improved millions of lives worldwide," said Mr. Pien. "We have made these great strides because of our commitment to protecting people through innovative science. This sense of mission will continue to motivate employees in the future."

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.