Gilead Sciences to be Added to S&P 500 Index

FOSTER CITY, Calif.--(BUSINESS WIRE)--June 23, 2004--Gilead Sciences, Inc. (Nasdaq:GILD) today announced that Standard & Poor's will include the company in the S&P 500 Index at the close of trading on Wednesday, June 30, 2004. Gilead will be added to the S&P 500 Global Industry Classification Standard (GICS) Biotechnology Sub-Industry Index.

The S&P 500 Index consists of 500 stocks chosen for market size, liquidity and industry group representation. It is a market-value weighted index (stock price times number of shares outstanding), with each stock's weight in the index proportionate to its market value. According to Standard and Poor's, the "500" is one of the most widely used benchmarks of U.S. equity performance and is held broadly by U.S. and international index funds.

Gilead Sciences

Gilead Sciences is a biopharmaceutical company that discovers, develops and commercializes therapeutics to advance the care of patients suffering from life-threatening diseases worldwide. The company has six marketed products and focuses its research and clinical programs on anti-infectives. Headquartered in Foster City, CA, Gilead has operations in the United States, Europe and Australia.

Susan Hubbard

650-522-5715

(Investors)

Amy Flood

650-522-5643

(Media)