Cephalon, Inc. Added to the Nasdaq-100 Stock Index

West Chester, PA - December 17, 2001

Cephalon, Inc., an international biopharmaceutical company, today announced that it was be added to the Nasdaq-100 Index® effective with the market open on Monday, December 24, 2001.

The Nasdaq-100 Index is composed of 100 of the largest non-financial companies listed on the Nasdaq National Market tier of The Nasdaq Stock Market. The index was first published in January of 1985 and has achieved wide acceptance by both investors and market professionals. It reflects Nasdaq's largest companies across major industry groups, including computer and office equipment, computer software/services, telecommunications, retail/wholesale trade, and biotechnology.

"Cephalon is honored to be included in the Nasdaq-100," Frank Baldino, Jr., Ph.D., chairman and CEO of Cephalon, said. "This year -- 2001 -- has been the most successful in the history of our company. The addition of Cephalon to the Nasdaq-100 Index is further recognition of our tremendous growth and achievements, which include record product sales, profitability and international expansion of our business."

Cephalon shares now will be included in the Nasdaq-100 Index Tracking Stock(SM) , which investors can purchase as they would any other stock listed on The American Stock Exchange. The Nasdaq-100 Tracking Stock is a one-investment portfolio that gives investors ownership in all of the stocks of the Nasdaq-100 Index and aims to provide investment results that generally correspond with its performance.

Cephalon, Inc., headquartered in West Chester, Pennsylvania, is an international biopharmaceutical company that discovers, develops and markets products to treat neurological and sleep disorders, cancer and pain. The company currently markets its three proprietary products in the United States and nine products internationally. Cephalon develops innovative products for the treatment of neurological diseases and cancer through identification of novel compounds that affect both cell survival and death. Additional information about Cephalon can be obtained by visiting the company's website at www.cephalon.com.