Robert J. Familton, 55, the deputy treasurer of the International Monetary Fund and a former president of the Eastern and Potomac Rugby unions, died of cardiac arrest Dec. 25 at Suburban Hospital.

Mr. Familton, who lived in Bethesda, was born in Christchurch, New Zealand. He was educated at St. Andrews College and Canterbury University, where he received a master's degree in economics in 1948. From 1952 to 1953, he held a Fulbright scholarship to the University of California at Berkeley.

He worked for the Reserve Bank of New Zealand until 1962, when he moved to Washington and joined the IMF. He specialized in the economies of Eastern Europe and became a division chief in the Fund's exchange and trade relations department. He joined the treasurer's department in 1969 and was named deputy treasurer in 1970.

Mr. Familton played rugby in college and coached the Washington Rugby Football Club. He also was a founder of the IMF's staff facility, the Bretton Woods Recreation Center in Germantown.

Survivors include his wife, Joan M. Familton, of Bethesda, two sons, John of Auckland, New Zealand, and Richard of Bethesda; a daughter, Vicki Hughes of Cape Canaveral, and a sister and a brother in New Zealand.