Donald St. Claire Matheson Sr., 73, who retired from the Department of Agriculture in 1975 as head of its fresh fruits and vegetables inspection program, died of cardiac arrest Wednesday at Georgetown University Hospital.

Mr. Matheson, who was born at Max Meadows, Va., graduated from Presbyterian College in North Carolina. He became a high school teacher and principal in that state.

One summer, he took a part-time job as an inspector with the Agriculture Department. In 1933, he decided to make it his career. In 1935, he became a full-time fresh fruit and vegetable inspector. He worked in New York City, Virginia, North Carolina and Chicago, where he was assistant distributor supervisor.

Four years later, in 1950, he was transfeered to Washington as assistant chief of the fresh fruit and vegetable inspection branch. He was named branch chief in 1964 and held that post until he retired.

Mr. Matheson, who lived in Falls Church, was a member of the Westwood Country Club.

His wife, Margaret Moore Matheson, died in 1971.

Survivors include two sons, Donald S. Jr., of Falls Church, and Gordon M., of Golden, Colo.; two brothers, R. Gordon, of Paducah, Ky., and Douglas, of Raleigh, N.C., and two grandchildren.