Dr. Joseph V. Kennedy, 81, a former president of the D.C. Medical Society and a dermatologist in Washington until he retired in 1977 after 50 years of practice, died at his home in Washington Feb. 7 after a heart attack.

Dr. Kennedy was born in Lawrence, Mass. He graduated from Forham University and moved here in the early 1920s to attend the Georgetown University medical school, where he graduated in 1927. He studied at Columbia University in New York and was chief resident at the old Gallinger Hospital here.

In addition to his practice, Dr. Kennedy was a physician in the Selective Service System here in World War II. He taught at the Georgetown medical school in the 1940s and early 1950s and was a director of the old Doctors Hospital. He received a medal from President Truman for his work with Selective Service.

Dr. Kennedy was a diplomate of the American College of Dermatology and a member of the American Academy of Dermatology, the American Medical Association and the Southern Medical Society.

He was a former president of the Merrick Boys Camp and a life member of the Columbia Country Club and the Friendly Sons of St. Patrick.

His wife, Christine O'Neill Kennedy, died in 1976.

Survivors include two daughters, Christine O'Connor of Acton, Mass., and Susan Murphy of Cumberland, R.I.; two sons, Dr. J. Neill Kennedy of Washington, and Edward B. Kennedy of Alexandria; a sister, Louise Gallagher of Hampton, N.H., and 11 grandchildren.