William J. Kirby, 62, who retired as manager of the Bethesda Post Office in 1973 after 38 years of federal service, died Tuesday at Suburban Hospital in Bethesda after a heart attack.

a native of Washington, Mr. Kirby joined the postal department in 1935 after graduating from St. John's College High School. He started out as a postal clerk and later became manager of post office branches in Washington, Chevy Chase, and Bethesda.

He enlisted in the Army in 1942 and served in the 745th Military Police Battalion in the South Pacific during World War II.

Mr. Kirby lived in Bethesda and was active in the Holy Name Society at St. Catherine Laboure Catholic Church in Wheaton. He was a member of the Rosensteel Council of the Knights of Columbus, the Fitzgerald Cantrell American Legion Post No. 105 in Bethesda, the Ancient Order of Hibernians, the Irish-American Club, the Loyal Retired League, Chapter 260 of the National Association of Retired Federal Employes and the National Association of Postal Supervisors.

Survivors include his wife, Rebecca P., of the home in Bethesda, and a sister, Mary Wilkinson, of Arlington.

The family suggests that expressions of sympathy be in the form of contributions to the Heart Memorial Fund of Montgomery County