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                                                                    EXHIBIT 99.1


Contact:          Jason Rubin                                   Larry Kurtz
                  Cephalon, Inc.                                Chiron Corp.
                  (610) 344-0200                                (510) 923-2476



FOR IMMEDIATE RELEASE



                   Cephalon and Chiron Announce Results of FDA
                           Advisory Committee Meeting

         West Chester, Pa., and Emeryville, Calif. - May 8, 1997 - The U.S.
Food and Drug Administration's (FDA) Peripheral and Central Nervous Systems
Drugs Advisory Committee today found, by a vote of 6 to 3, that there was not
substantial evidence that MYOTROPHIN(R) (rhIGF-1 or mecasermin) Injection is
effective in the treatment of amyotrophic lateral sclerosis (ALS or Lou Gehrig's
disease). The committee's finding was requested by the FDA in conjunction with
its review of a New Drug Application (NDA) submitted by Cephalon, Inc.
(NASDAQ:CEPH) and Chiron Corp. (NASDAQ:CHIR) for clearance to market MYOTROPHIN
Injection for the treatment of ALS.

         In response to the committee's vote, Frank Baldino, Jr., Ph.D.,
Cephalon's president and chief executive officer, and William Rutter, Ph.D.,
Chiron's chairman, stated, "We are deeply disappointed with the committee's
finding about MYOTROPHIN Injection. We appreciate the many expressions of
support from patients, caregivers and physicians and will be reviewing with the
FDA the panel's recommendation."

         Cephalon, Inc., headquartered in West Chester, PA, is an international
biopharmaceutical company that discovers, develops and markets products to treat
neurological disorders. The company is developing products for the treatment of
ALS, narcolepsy, peripheral neuropathies, Alzheimer's disease, head and spinal
injury, and stroke, and currently copromotes two products in the United States
for the treatment of neurological conditions.

         Chiron Corporation, headquartered in Emeryville, Calif., near San
Francisco, is a science-driven, market-directed healthcare company that
combines diagnostic, vaccine and therapeutic strategies for controlling disease.
Chiron participates in four global healthcare markets: diagnostics, including
immunodiagnostics, critical care diagnostics and new quantitative probe tests;
therapeutics, with an emphasis on oncological, infectious, neurological and
cardiovascular disease; pediatric and adult vaccines; and ophthalmic surgical
products for the correction of vision. Chiron also conducts research and
development in the fields of biological proteins, gene therapy and combinatorial
chemistry.

         This news release may contain forward-looking statements that involve
risks and uncertainties. A full discussion of the companies' operations and
financial condition, including factors that may affect their business and future
prospects, is contained in documents the companies file with the SEC, such as
form 10-Q and 10-K reports. These documents identify important factors that
could cause the companies' actual performance to differ from current
expectations.