Donald E. Smith, 50, an associate editor of U.S. News & World Report and a member of the magazine's staff for more than 20 years, died Wednesday after an apparent heart attack at his home in Washington.

Mr. Smith had been editor of the magazine's News You Can Use column for the past four years.In 1975, he received an award from the National Headliners Club for a "consistently outstanding magazine feature column."

He joined U.S. News & World Report in 1953 as an assistant makeup editor. He later switched to reporting and was assigned to Capitol Hill, where he covered legislation, postal and Social Security matters.

He was chairman of the executive committee of the Congressional Periodical Press Gallery in 1973.

Mr. Smith also was a member of the White House Correspondents Association.

He was born in Canandaigua, N.Y., and grew up there. He spent two years in the Army. He came to Washington following World War II to attend Catholic University, from which he graduated in 1950. He then worked toward a master's degree and was a clerk in various stores before joining U.S. News & World Report.

Survivors include his wife, Barbara, and two children, Karen and Mark, all of the home, and a brother, Gerald A. Smith, of Geneseo, N.Y.