Edwin K. Pratt, 52, a special agent in the FBI Washington field office since 1955, died Tuesday at his home in Wheaton after a long illness.

He had joined the FBI in 1950, and had served as a special agent in Charlotte, N.C., Baltimore and Albany, N.Y., before coming here.

Born in Cleveland, Mr. Pratt was a graduate of Kent State University and earned a law degree from Western Reserve University. He was a member of the Ohio Bar.

During World War II, he served in Europe as a gunner with the Army Air Corps. He was captured near the end of the war by Germans and was held prisoner until the Germans surrendered. He received the Air Medal.

Mr. Pratt was a member of Glenmont United Methodist Church in Wheaton.

He is survived by his wife, Miriam B., and two sons, Edwin A. and James M., all of the home: another son, William D., of Virginia Beach; two daughters, Laurel Anne Vaughan, of Adelphi, and Susan Lee Fierro, of Gaithersburg; his father, H. Duane Pratt, of Westminister, Calif., and a grandchild.

The family suggests that expressions of sympathy may be in the form of contributions to the memorial fund of Glenmont Methodist Church.