William T. McCormick, 65, a government official who specialized in foreign economic and military assistance and in civil defense, died at his home in Arlington on Saturday following a heart attack.

Mr. McCormick joined the government in 1941 and particpated in the World War II lend-lease program to provide arnaments to allies. After the war, he helped direct economic recovery programs for Europe and Asia, end of 1975, he was a program management analyst in the Defense Civil preparedness Agency.

Mr. McCormick was the Washington representative of Burn & Roe, Inc., an engineering firm, at the time of his death.

Mr. McCormick was born in Girardville, Pa. He came to Washington in 1932 to attend Georgetown University, from which he graduated in 1936. He earned a law degree from Georgetown in 1941.

His World War II assignment with the lend-lease administration dealt with providing supplies to the Soviet Union. His post-war duties were with the Foreign Economic Administration and the State Department in the field of foreign aid. In 1949, he was assigned to the Small Business Administration for the purpose of persuading American firms to take part in the foreign aid program. He also served as a aide to the House and Senate Select Committee on Small Business.

During this period, he founded the Contact Clearing House Service, the purpose of which is to stimulate foreign investments. The program was taken over by the Commerce Department.

When he returned to government in 1956 after working for three years as a private consultant on international investment oppportunities, he joined the Defense Department as an advisor to the Secretary of Defense on security in the Far East. He switched to civil defense in 1962 and remained in that field until his retirement.

Mr. McCormick was a resident of Arlington and was a member of St. Agnes Catholic Church. He also was a 4th degree member of the Knights of Columbus. He was a member of the Society of American Military Engineers.

Mr. McCormick married the former Lucy Valentine Offutt in 1940. She died in 1976.

Survivors include two sons, William T. Jr., of Great Falls, Va., and Brian J., of Gaithersburg; two daughters, Kathleen A., of Great Falls, and Lucy V. Gassaway, of Huntsville, Utah; four sisters, Mrs. Thomas Flaherty and Mrs. Bert Glick, of Washington, Mrs. Victor Anderson, of Girardville, Pa., and Mrs. Margaret Wishing, of Glen Riddle, Pa.; two brothers, Leo, of South Sterling, Pa., and Clair, of Williamsport, Pa., and two grandchildren.