Walter E. Smith 61, a retired State Department auditor, died of a heart attack Wednesday while visiting at the home of his brother-in-law, Eugene Collela, in Washington.

A former resident of Bethesda, Mr. Smith had moved to Boonton, N.J., last year.

From 1960 until his retirement in 1969, he had been senior foreign assistance inspector in the State Department's Office of the Inspector General of Foreign Assistance.

In that capacity, Mr. Smith had traveled extensively in Europe, Latin America, Africa and Asia, checking on the efficiency of this country's economic and military assistance.

Born in Rochester, Minn., he was a graduate of Augustana College. He joined the General Accounting Office here in 1941 as an assistant auditor, and then became an auditor and claims examiner.

In 1952, Mr. Smith transferred to the Department of the Army as an auditor and later was a budget officer and an administrative officer.

He joined the State Department in 1960 as senior auditor in the Office of the Inspector General and Controller.

He is survived by his wife, Yolande, and a daughter, Sharon S. Goode, both of the home in Boonton; a brother, James, of California; a sister, Frances Ballard, of Moline, Ill., and one grandchild.

The family suggests that expressions of sympathy may be in the form of contributions to the American Heart Association.