Fully Automated PROCLEIX TIGRIS System Approved for Use with PROCLEIX ULTRIO Assay.

EMERYVILLE, Calif. & SAN DIEGO -- CE Marking Clears Way for Commercialization of the System in European Union and Other Parts of the World

Chiron Corporation (Nasdaq:CHIR) and Gen-Probe Incorporated (Nasdaq:GPRO) today announced that the PROCLEIX(R) ULTRIO(TM) Assay for use on the PROCLEIX(R) TIGRIS(R) System has been granted the CE (Conformite Europeene) Mark in accordance with Directive 98/79/EC. With the CE Mark, the companies can now proceed with the commercialization of the PROCLEIX TIGRIS System in the European Union, as well as in other parts of the world that accept the CE Mark. The fully automated, high-throughput PROCLEIX TIGRIS System can process 1,000 blood samples in under 14 hours, facilitating testing in smaller pool sizes and individual donor testing.

"The launch of the PROCLEIX TIGRIS System outside the United States is an important milestone for the Chiron/Gen-Probe partnership," said Gene Walther, acting president, Chiron Blood Testing. "The PROCLEIX ULTRIO Assay and the PROCLEIX TIGRIS System provide a powerful combination of convenience and productivity. As we move into 2005, we expect that the PROCLEIX TIGRIS System, in conjunction with the PROCLEIX ULTRIO Assay, will provide blood centers throughout the European Union with the means to increase productivity and efficiency of their blood screening."

"The PROCLEIX TIGRIS System will revolutionize the blood screening industry with its state-of-the-art automation, throughput and process control," said Niall Conway, Gen-Probe's executive vice president, sales and operations. "In addition, the European launch of the system with the PROCLEIX ULTRIO Assay will be an important growth driver for Gen-Probe in 2005."

The approval allows the already CE Marked PROCLEIX ULTRIO Assay to be run on the fully automated, high-throughput PROCLEIX TIGRIS System. The PROCLEIX ULTRIO Assay was developed to simultaneously detect human immunodeficiency virus, type 1 (HIV-1), hepatitis C virus (HCV) and hepatitis B virus (HBV) in specimens from donated blood, plasma, organs and tissue.

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.

About Gen-Probe

Gen-Probe Incorporated is a global leader in the development, manufacture and marketing of rapid, accurate and cost-effective nucleic acid testing products for diagnosing human diseases and screening donated human blood. Using its patented NAT technologies, Gen-Probe has received FDA approvals or clearances for a broad portfolio of products that detect a variety of infectious microorganisms, including those causing sexually transmitted diseases, tuberculosis, strep throat, pneumonia and fungal infections. Additionally, the Company developed and manufactures the only FDA-approved blood screening assay for the simultaneous detection of HIV-1 and HCV, which is marketed by Chiron. Gen-Probe has more than 20 years of expertise in nucleic acid detection, and its products are used daily in clinical laboratories and blood collection centers throughout the world. Gen-Probe is headquartered in San Diego, California and employs approximately 900 people. For more information, go to www.gen-probe.com.

Forward-Looking Statements

This news release contains forward-looking statements, including statements regarding regulatory approval of the PROCLEIX ULTRIO Assay and the PROCLEIX TIGRIS System, sales growth, product development initiatives, new product indications, and new product marketing that involve risks and uncertainties and are subject to change. A full discussion of the companies' operations and financial conditions, including factors that may affect their businesses and future prospects, is contained in documents the companies have filed with the SEC, including the respective forms 10-Q for the quarter ended September 30, 2004, and the forms 10-K for the year ended December 31, 2003, and will be contained in all subsequent periodic filings made with the SEC. These documents identify important factors that could cause the companies' actual performance to differ from current expectations, including the outcome of clinical trials, regulatory review and approvals, manufacturing capabilities, intellectual property protections and defenses, stock-price and interest-rate volatility, and marketing effectiveness. In particular, there can be no assurance that the companies will increase sales of existing products, successfully develop and receive approval to market new products, or achieve market acceptance for such new products. There can be no assurance that out-licensing activities will generate significant revenue, nor that in-licensing activities will fully protect the companies from claims of infringement by third parties. In addition, the companies may engage in business opportunities, the successful completion of which are subject to certain risks, including shareholder and regulatory approvals and the integration of operations.

Consistent with SEC Regulation FD, we do not undertake an obligation to update the forward-looking information we are giving today.

Note: PROCLEIX and ULTRIO are registered trademarks of Chiron Corporation. TIGRIS is a registered trademark of Gen-Probe Incorporated.