Foster Osgood Chanock, 28, a White House aide during the presidency of Gerald R. Ford died of cancer Saturday at the National Insttutes of Health.

Mr. Chanock joined the White House staff in 1975 as assistant to the White House Chief of Staff. In that capacity he served under both Donald Rumsfeld and Richard B. Cheney, who now is a Republican congressman from Wyoming.

In addition to his staff work in the White House, Mr. Chanock was active in Ford's election campaign in 1976 and helped plan the presidential debates that year.

Mr. Chanock was born in Cincinnati and reared in Bethesda. He was a graduate of Sidwell Friends School. He earned a bachelor's and master's degrees in telecommunications at the University of Chicago in 1974 and spent a year at the London School of Economics. He then joined the White House.

It was while he was in Europe that Mr. Chanock met Donald Rumsfeld and expressed interest in working in the White House. Mr. Chanock was hired for a 90-day tryout and stayed on until the Carter administration began on Jan. 20, 1977.

In January 1977, Mr. Chanock joined the First Boston Corporation, an investment banking firm, in New York City. He was an associate in First Boston's corporate finance department at the time of his death.

Survivors include his wife, the former Dorothy Caeser of New York City; his parents, Dr. and Mrs. Robert M. Chanock, of Bethesda, and a brother, Stephen, of Brookline, Mass.

The family suggests that expressions of sympathy be in the form of contributions to Children's Hospital.