George Milton Gilbert, 55, a retired insurance executive with the Harris Agency in Arlington and a resident of Falls Church since 1946, died Tuesday at Fairfax Hospital after a heart attack.

Mr. Gilbert joined the Harris Agency, formerly the G.H. Rucker Co., in 1957 and retired as president of the insurance department earlier this year. Before joining the agency, he was an insurance agent for several national insurance firms. From 1950 to 1953, he worked for the old National Production Authority of the Department of Commerce.

During and after World War II, he served with the Army in Europe. He joined the Army reserve in 1949 and retired with the rank of colonel in 1979.

Mr. Gilbert was a native of Bronson, Fla. He attended the University of Florida and was a 1949 graduate of George Washington University here.

He was a member of the Westmoreland Community Church in McLean, the Arlington Temple and the Arlington Rosslyn Lions Club.

His wife, Betty Lou George Gilbert, died in 1961.

Survivors include a daughter, Mary Elissa Gilbert Fallon of Sterling, Va.; a son, John Milton of Falls Church; a brother, Carroll of Bronson; four sisters, Myrtie Hardee of Bronson, Inez Brown of Beaufort, S.C., Eva Stokes of Ocala, Fla., and Ella Mae Gilbert of Miami, and one grandchild.