William J. McCahill, 89, a retired executive with the International Harvester Co. and a volunteer in behalf of retarded and physically handicapped children here for the last 20 years, died Saturday at the Manor Care Nursing Center in Arlington after a brief illness. He lived in North Arlington.

Mr. McCahill worked for International Harvester's motor truck division for 40 years, from 1912 to 1952. He served briefly in the Government and worked as assistant to the president of the Kenosha Auto Transport Co. before moving to Arlington in 1958, where he carried on a wide range of volunteer activities to assist the handicapped.

From 1967 to 1977 he worked several days a week as a volunteer consultant for the People to CPeople Committee for the Handicapped and received their "Volunteer of the Year" award at an annual meeting of the President's Committee on. Employment of the Handicapped several years ago.

He was named Catholic Layman of the year by the Catholic War Veterans of Virginia in 1965.

As part of his volunteer work, he helped arrange for the delivery of wheelchairs to individuals and groups in more than a dozen foreign countries.

Mr. McCahill was born in Cincinnati, and studied at Canisius College Academy in Buffalo, N.Y. He served from 1905 to 1912 with the 71st Infantry of New York's National Guard.

Survivors include two sons, Col. William P. and John L., both of Arlington.

The family suggests that expressions of sympathy be in the form of donations to St. Coletta's School, 1305 N. Jackson St., Arlington.