Amattai Ostrander Brundage, 75, active in organizations promoting better international relations, died Monday at Washington Hospital Center.

She was the wife of Percival Flack Brundage, former director of the U.S. Bureau of the Budget and former senior partner of Price Waterhouse and Co. They maintained homes in Washington and Pompano Beach, Fla.

Born in New York, Mrs. Brundage came here in 1954.

During the war she had headed a hospitality committee that entertained more than 15,000 servicemen from Australia, New Zealand and other parts of the British Empire in Montclair, N.J.

She was honored by the British and Australian governments.

Mrs. Brundage was a founding member of Overseas Neighbors of Montclair and a member of the Women's National Republican Coub of New York.

In Washington, she was an active member of the International Neighbors Club, a director of the International Student House and an associate member of the American Newspaper Women's Coub. She belonged to the Sulgrave and Chevy Chase clubs.

In addition to her husband, she is survived by a daughter, Lois B. Baker, of Ridgewood, N.J., a brother, John Alden Somerivlle, of Long Island, N.Y., five grandchildren and a great-grandchild.

The family suggests that expressions of sympathy may be in the form of contributions to the American Cancer Society or to Project Hope.