William Lawrence Hebbard, 66, who retired a year ago as secretary of the International Monetary Fund, died of cancer Monday at Georgetown University Hospital.

He had joined the IMP in 1954, as a division chief in the exchange and trade relations department and was named assistant director of the department in 1957. During that period, he worked on the General Agreement on Tariffs and Trade and headed consulation missions to a number of countries.

Mr. Hebbard transferred to the secretary's department in 1964 as deputy secretary of the fund. He became secretary in 1967.

Born in Ishpeming, Mich, he was a graduate of the University of Michigan, where he also earned a master's degree in economics and was a teaching fellow and research assistant. He later attended the Graduate School for International Studies in Geneva, Switzerland, and was assistant to the director of the Geneva Research Center.

He came to Washington as a Michigan-Brookings Fellow in 1940, when he joined the Treasury Department. His work involved British investments and the Lend-Lease program.

In 1941, Mr. Hebbard became a member of the Foreign Funds Control Team, stationed in Honolulu and then Manila. He was interned in the Philippines from 1942 to 1945 under the Japanese occupation.

Returning to the Treasury Department here, he was appointed chief of its British Comonwealth division. From 1948 to 1950, he was the department's representative in London. He also served as financial attache at the U.S. Embassy and as head of the financial division of the Marshall Plan.

Mr. Hebbard was assistant director of the Office of International Finance at the Treasury Department from 1950 until joining the IMF.

He is survied by his wife, Ethel, of the home in Kensington; two daughters, Barbara Bowman, of Berkeley, Calif., and Patricia Hebbard, at the University of Maryland; a son, Bruce, at the University of Michigan, and one grandchild.

The family suggests that expressions of sympathy may be in the form of contributions to the Vincent T. Lombardi Cancer Center at Georgetown University Hospital.