Dr. Joseph Seifter, 77, a physician who was senior medical adviser in the Environmental Protection Agency's office of toxic substances and a research professor in pharmacology at the George Washington University medical school, died June 2 at George Washington University Hospital after a heart attack. He lived in Alexandria.

Dr. Seifter was born in Czechoslovakia and reared in Cleveland. He was a 1934 graduate of the Emory University medical school. From 1944 to 1962, he worked for the Wyeth pharmaceutical company in Philadelphia, where he became director of basic medical science research.

He was research professor of pharmacology at the New York Medical College for 14 years before moving to Washington and joining EPA in 1976. He had taught at GW since 1980.

Dr. Seifter did work in industrial toxicology, anticoagulants and psychopharmacology. He was a member of NASA's National Toxicological Board and a consultant to the National Heart Institute. He was a charter member of the Society of Toxicology.

Survivors include his wife, Mathille, of Alexandria; three brothers, Eli, of New Hyde Park, N.Y., Sam, of New Rochelle, N.Y., and Benjamin, of Cleveland, and four sisters, Gertrude Nash, Mary Rubin, Frances Hohauser, and Esther Mathews, all of Cleveland.