Robert L. Wolff '36, Coolidge Professor of History and lecturer in History 1270, "The Byzantine Empire," and History 1570, "The Ottoman Empire and the Middle East since the Thirteenth Century," died Tuesday night of an apparent heart attack. He was 64 years old.

Wallace MacCaffrey, Higginson Professor of History and current chairman of the History Department, announced the news of Wolff's death to students in the History 1270 class yesterday morning. Wolff had been hospitalized a month ago for pneumonia, but he told his class recently that his doctor had given him a clean bill of health, only warning him not to exert himself.

A member of the Harvard faculty for 30 years, Wolff was an expert on the Balkans and the Byzantine Empire.

During World War II he served as assistant to the director of the Balkan section of the Office of Strategic Services (OSS). He was best known for his book "The Balkans in Our Times."

Wolff also amassed one of the world's largest collections of 19th century English novels and at the time of his death was editing a series of reprints of Irish novels.

He authored the two-volume "History of Civilization," a standard high school and college history textbook.

Born in New York City on December 26, 1915, Wolff received his bachelors and masters degrees at Harvard. He became a teaching fellow here in 1937 but left to join the OSS in 1941. After the war he taught for four years at the University of Wisconsin.

He returned to Harvard as associate professor in 1950, became a full professor in 1955, and was chairman of the History Department from 1960-1963.

Frank B. Freidel, Warren Professor of American History, said yesterday he was "shocked to hear of the death of this delightful and charming man." Freidel called Wolff "a brilliant scholar, a man of incomparable erudition."

"Wolff's teaching duties in History 1270 will probably be assumed by Dennis Skiotis, associate director of the Center for Middle Eastern Studies, MacCaffrey said.