Dr. Louis Gillespie Jr., 52, an internist and cardiologist in Washington and a former chairman of the board of governors of the American College of Cardiology, died Sunday at the Washington Hospital Center. He had a lung ailment.

Dr. Gillespie, who was born in New York City, graduated from the Taft School in Watertown, Conn. He took his bachelor's and medical degrees at Western Reserve University in Cleveland. He did his internship and residency at the University Hospitals in Cleveland.

In 1957, he moved to the Washington area and became a clinical associate and senior clinical investigator at the National Heart Institute of the National Institutes of Health, now the National Heart, Lung and Blood Institute of NIH. In 1962, he established a private practice in internal medicine and cardiology in Washington and continued it until his death.

Dr. Gillespie was a senior attending physician at the Washington Hospital Center, a member of its board of trustees and the president of its medical and dental staff from 1977 to 1980.

After serving as chairman of the board of the American College of Cardiology, he became its treasurer, a position he held at the time of his death.

Dr. Gillespie was a member of the American Medical Association, the Federation for Clinical Research and the American Heart Association. He was a fellow of the American College of Physicians.

He lived in Chevy Chase and was a member of the Bethesda Country club.

Dr. Gillespie's survivors include his wife, Nancy, of Chevy Chase; two daughters, Coille C. and Pamela Way, both of Chevy Chase; two sons, Colin D., of Chevy Chase, and Kevin Bennett, of Bethesda, and a brother, E. S. B. Gillespie of Boston.

The family suggests that expressions of sympathy be in the form of contributions to the Louis Gillespie Memorial, c/o The Washington Hospital Center.