Frederick C. Belen, 85, a former deputy U.S. postmaster general and chairman of the committee whose studies led to use of the Zip code system, died Oct. 13 at Arlington Hospital. He had Parkinson's disease.

Mr. Belen, who lived in Arlington County, was assistant postmaster general for operations before being named to the second-highest job at what was then the Post Office Department during the Johnson administration. He helped initiate and oversee automation of the Post Office, using the Zip code system of numbers for towns and cities and a network of regional distribution centers.

He began his Washington career on Capitol Hill, where he was secretary to two Michigan Democrats, Reps. Andrew J. Transue and George D. O'Brien, prior to World War II. He was chief counsel and staff director of the House Post Office and Civil Service Committee before being named assistant postmaster general during the Kennedy administration.

Mr. Belen was a native of Lansing, Mich., and a graduate of Michigan State University. He received a law degree from George Washington University.

He served in the Army during World War II and helped establish a wartime security system for the Pentagon and Army embarkation ports.

Mr. Belen went into private law practice in 1969, specializing in legislative and postal issues. His clients included the United Parcel Service.

Mr. Belen was president of the National Democratic Club in the mid-1970s. He was a trustee and elder of Little Falls Presbyterian Church in Arlington, president of the Michigan State Society and a member of the American Society for Public Administration, the Arlington Council of the Boy Scouts of America, the American Legion and the Disabled American Veterans. He had a second home in Coles Point, Va.

His honors included the Post Office's first Benjamin Franklin Award for leadership and a Distinguished Civilian Service Award from the Army.

Survivors include his wife of 56 years, Opal Sheets Belen of Arlington and Coles Point; a son, Frederick C. Belen Jr. of Herndon; a sister; and three grandchildren.