John Gail Maier, 55, a former chairman of the department of radiation at Fairfax Hospital and radiology specialist with the Army Medical Corps for 20 years, died of cancer June 3 at Fairfax Hospital.

Dr. Maier, who lived in Potomac, was born in St. Louis and graduated from the St. Louis School of Medicine in 1952. He later earned a doctorate in radiation biology from the Rochester University School of Medicine and Dentistry.

He came to Washington in 1952 and joined the Army Medical Corps at Walter Reed Army Medical Center, where his staff positions included chairman of the department of radiology, chief of the division of radiation oncology, and chief of the division of nuclear medicine. He was commander of the 91st Evacuation Hospital in Vietnam in 1966 and 1967. He retired from the Army as a colonel in 1972.

Dr. Maier then served as a clinical professor or radiology at George Washington University Hospital until 1977, and as chairman of the department of radiation at Fairfax Hospital from 1977 until retired in 1982.

His military honors included the Legion of Merit. He was also a Fellow of the American College of Radiology.

Survivors include his wife, Sara, of Potomac; a daughter, Ann Marie of Gaithersburg; four sons, Aaron and Paul, both of Potomac, Matthew of Gaithersburg, and Michael of Denver; and his mother, Marie Maier of Rockville.