Dr. Robert St. Gordon Jr., 59, a special assistant to the director of the National Institutes of Health since 1976 who also had served as an assistant surgeon general of the U.S. Public Health Service, died of cancer Aug. 2 at his home in Kensington.

Dr. Gordon was born in New York City. He was a graduate of Harvard University and its medical school. He earned a master's degree in epidemiology from the Johns Hopkins School of Hygiene and Public Health.

He joined NIH in 1953 as a clinical associate in what became the National Heart, Lung and Blood Institute. In 1961, he helped develop a cholera research program in what became Bangladesh. He returned to NIH in 1964, and served as clinical director of the National Institute of Arthritis and Metabolic Diseases, and then as director of NIH's clinical center.

In 1982, Dr. Gordon organized the NIH Working Group on acquired immune deficiency syndrome (AIDS), and became the key coordinator at NIH for AIDS research.

He was a past president of the Society for Clinical Trials, of which he was a past president. He was a member of the American College of Epidemiology, the Society for Epidemiologic Research. He was a recipient of the Department of Health and Human Services exceptional achivement award, and the Stouffer Award, presented by the Stouffer food company.

He was a member of St. Luke's Episcopal Church in Bethesda.

Survivors include his wife, Elizabeth, of Kensington; two sons, Dr. Andrew S., of Norfolk, and Dr. Peter T., of Portland, Me.; two daughters, Dana Dixon of Cleveland, and Hilary Gordon of San Francisco; his mother, Dorothy Gordon of Chevy Chase; a brother, Dr. James P., of Rumson, N.J., and three grandchildren.