Dr. Roy Lyman Sexton, 85, a retired Washington physician who specialized in internal medicine, died Friday at his home here after a stroke.

He had maintained offices at 1801 I St. NW for most of his career, which spanned 53 years before he retired in 1972.

Dr. Sexton had been one of the first physicians here to use the gastroscope, an instrument for visually observing diseases of the stomach, and had trained other doctors in its use.

In 1949, he became the first person to televise, without surgery, the inside of the human stomach, using a gastroscope. The demonstration was given before a small group of doctors attending an American Medical Association meeting here. TDr. Sexton had been a consultant in gastroenterology and a member of the board of directors of Doctors Hospital since 1939. He had served as editor of the Journal of the American Gastroscopic Society for 11 years.

From 1930 to 1955, he was medical adviser to the secretary of the Interior and a consultant to the Bureau of Indian Affairs, the National Park Service and the Fish and Wildlife Service. He received a Distinguished Service Award from the Interior Department. He also had been a medical consultant to the State Department.

Dr. Sexton was born in Washington. He was a graduate of Central High School and the Georgetown University School of Medicine.

He had served for many years as chairman of safety services for the D.C. chapter of the American Red Cross and was on its board of directors.

From 1965 to 1975, he was a part-time medical director, physician and lecturer on the scientific cruise ship, Lindblad Explorer, and logged 450,000 nautical miles.

A 32nd degree Mason, Dr. Sexton was a member of the Metropolitan Washington Board of Trade, the Kiwanis Club, the University Club, the Potomac Appalachian Trail Club and the D.C. Medical Society.

He is survived by a son, Roy L. Jr., of Silver Spring a daughter, Jean Clarke, of Washington, five grandchildren and two great-grandchildren.

His sister, Dora B. Speaker, a former Washington resident, died Thursday in Palm Beach, Fla.

The family suggests that expressions of sympathy be in the form of contributions to the D.C. chapter of the American Red Cross. CAPTION: Picture, DR. ROY L. SEXTON