S. Harrison Kahn, 69, a Washington attorney since 1933 who specialized in laws involving the trucking industry and other motor carriers, died of cancer Thursday at his home in Arlington.

Mr. Kahn was born in Portsmouth, Va., graduated from the University of Virginia, and earned his law degree at the University of Chicago. He moved to Washington in 1933 and went to work for one of the New Deal government agencies.

In 1935, he went into private practice and specialized in representing bus and trucking companies before the Interstate Commerce Commission and other regulatory agencies. Except for World War II service in the Pacific in the Navy, he continued his practice until his death. For the past six years, Mr. Kahn had been in partnership with his son, Jeremy in the firm of Kahn & Kahn with offices in Washington. He was the first counsel of the National Tour Brokers Association, an industry trade group which he helped organize.

Mr. Kahn was a founding member of the Motor Carrier Lawyers' Association and served as the organization's national president in 1955.

He was active in alumni affairs of the University of Virginia and was a member of the Washington Hebrew Congregation and its Brotherhood.

In addition to Jeremy Kahn of Chevy Chase, survivors include his wife, Hannah of Arlington; two daughters, Dana Jo Mermelstein of Silver Spring, and Hermine Kahn of New York City; a sister, Mrs. Nathan Lester of Danville, Va., and three grandchildren.

The family suggests that expressions of sympathy be in form of contributions to the Washington Area Merit Scholarship Fund, the University of Virginia, Charlottesville, Va.