Corcoran Thom Jr., 78, a retired senior vice president of the Riggs National Bank who was active in civic, cultural, volunteer and social organizations, died March 3 at the Washington Hospital Center as a result of injuries suffered in a fire at his home in Washington on Feb. 28.

A spokesman for the D.C. Fire Department said Mr. Thom had apparently fallen asleep in a chair while smoking a cigarette.

Mr. Thom began his career with Riggs in 1928. He rose through the ranks to become assistant manager of the Dupont Circle branch, vice president, and finally senior vice president. He retired in 1971.

He also was a member of the board of what is now USAir and in 1979 retired as chairman of the airline's finance committee. He served on the board of the Association of Reserve City Bankers and was a member of the Greater Washington Board of Trade. He was a founder and past president of the Junior Board of Commerce.

Mr. Thom was a life trustee of the Corcoran Art Gallery and had been chairman of its finance committee. His father, the late Corcoran Thom Sr., a retired board chairman of the American Security & Trust Co., had served as the gallery's president. A great-great-uncle, William Wilson Corcoran, founded the gallery.

Mr. Thom also was on the boards of the Columbia Hospital for Women and Children's Hospital, and had been treasurer of both the Air Force Aid Society and the Washington Monument Society. He was a director of the D.C. chapter of the American Red Cross and had chaired local campaigns for the American Cancer Society.

He was a past president of the Metropolitan and Alfalfa clubs in Washington and had been a member of the Alibi and University clubs and Burning Tree Country Club. He also belonged to the Society of the Friendly Sons of St. Patrick.

Mr. Thom was a lifelong area resident and a 1928 graduate of Harvard University. He was an Army Air Forces combat intelligence officer in the Pacific during World War II, earning the Air Medal and attaining the rank of lieutenant colonel.

Survivors include his wife, the former Eliza H. Mitchell, whom he married in 1936, of Washington.