Dr. Frank S. Bacon, 73, a retired internist and a past president of the D.C. Medical Society, died of cancer Wednesday at Rappahannock General Hospital in Kilmarnock, Va.

He had moved to Kilmarnock after retiring in 1971 from his Washington practice, which he had maintained since 1946.

Dr. Bacon also had been on the senior advisory staff in internal medicine at the Washington Hospital Center and had been an associate clinical professor of medicine at George Washington University's School of Medicine.

He was president of the D.C. Medical Society during 1969-70 and also was a former president of the D.C. Society of Internal Medicine.

Dr. Bacon was born in Milaca, Minn. He graduated from the University of Minnesota in 1928 and earned a medical degree from the university's School of Medicine in 1931.

After interning at Letterman General Hospital in San Francisco, he became a staff member at the Veterans Administration hospital in Hampton, Va. He transferred in 1935 to the old Mount Alto Hospital, which was the Veterans Administration hospital in Washington, and remained there through most of 1946, serving as chief medical officer during the last year of his tenure.

During World War II, Dr. Bacon was on active duty with the Army but remained on the Mount Alto staff.

He did not practice medicine after moving to Kilmarnock, but was associated with the Northern Neck Medical Association, of which he became president. He also was associated with Northern Neck Bloodmobile operations and the Virginia Area 5 Health Services Agency. He was a consultant to Rappahannock Hospital.

Dr. Bacon also belonged to the Association of Military Surgeons, the American Society of Internal Medicine, and the American Heart Association. He was a fellow of the American College of Physicians.

He had been a charter member of the Virginia Peninsula Academy of Medicine and had been active in the D.C. and American public health associations.

He is survived by his wife, Lucille, and a daughter, Frances C., both of the home in Kilmarnock; another daughter, Mary E. Setzler, of Phoenix, Ariz.; a son, John e., of Chevy chase; a sister, Harriet Hales, of Morgantown, W. Va., aan seven grandchildren CAPTION: Picture, Frank S. Bacon