Retired Army Col. John I. Hincke Jr., 51, a decorated veteran who served two tours of duty in Vietnam, died of cancer Friday at Bethesda Naval Hospital. He was a resident of Potomac.

Col. Hincke was born in the Philippines and graduated from the U.S. Military Academy at West Point in 1954. He was an infantry officer in the Panama Canal Zone and taught mathematics at West Point before going to Vietnam.

He spent two tours as an adviser to the Army of South Vietnam, first in the mid-1960s and again in the early 1970s. During these tours he earned two Legions of Merit, the Bronze Star and Air Medals.

After his second stint in Vietnam, he came to Washington and served on the staff of the Arms Control and Disarmament Agency before retiring from active duty for reasons of health in 1978.

Col. Hincke was a graduate of the Army's Command and Staff School, the Naval War College, and earned a master's degree at the University of Maryland.After retiring from the Army, he studied for a time at the Virginia Theological Seminary in Alexandria.

He was a member and vestryman at Christ Episcopal Church in Rockville.

Survivors include his wife, Cecelia T., of Potomac, three daughters, Karyn, Sandra, and Lynda, also of Potomac; two sons, John III, of Wheaton, and Robert, of Rockville; his parents, retired Army Col. John I. and Mae K. Hincke, both of Washington, and two sisters, Catherine Sells of Arlington, and Caroline Hellmuth of Colorado Springs, Col.

The family suggests that expressions of sympathy be in the form of contributions to the memorial fund of the Christ Episcopal Church in Rockville.