Born in Glasgow. Educated at Strathallan School and St John's College, Cambridge, receiving his medical training at the Middlesex Hospital, graduating in 1936.
After house appointments at the Middlesex and Brompton, he was appointed resident assistant physician at St George's in 1939, an appointment which was to mark the beginning of a lifelong association. During the war years he found himself virtually running medicine at St George's, with a heavy load of ward, outpatient and teaching duties. Later in the war he organisex medical support for the surgical teams sent to Cosham, near Portsmouth, to receive casualties from the D-day beach head invasion. Casualties were few and he found time to do some teaching and relaxation on the beaches. At that time bombs were falling on Hyde Park Corner and he received a telegram saying 'From the trenches of Hyde Park we salute the heroes of Cosham!'
In 1946 He was appointed honorary assistant physician to St George's, and, after two years of National Service in the Army, settled down to pursue his medical career.
His talents were now employed in the development of the new St George's Hospital. Together with a few of his colleagues he had the vision to see that the future of the hospital lay elsewhere than Hyde Park Corner: a teaching hospital ought to function as a general hospital serving a large and varied population. In 1950, James Dow moved his firm to the Grove Fever Hospital, Tooting, and established a first class medical and gastroenterological unit there. He returned to Hyde Park Corner when some medical units had to be sent back there to facilitate the building of the new medical school at Tooting. He served as chairman of the medical advisory committee and as a member of the board of governors and as one of the special trustees.
He also served Wimbledon Hospital, was chairman of the medical committee of King Edward VII Hospital for Officers (Sister Agnes), and an examiner in medicine at Cambridge and the Royal College of Physicians. He was adviser to the London Life Assurance, and a member of the Association of Physicians of Great Britain and Ireland.
His first marriage ended with the early death of his wife Moira, who left him with an infant daughter. His second wife, Jean, a consultant radiologist, survived him, as did their four children.