Jimmy Tremayne was born at Pietermaritzburg, Natal, where his parents were temporarily domiciled while emigrating from Scotland to Australia. He spent his childhood at Stanhope in Northern Queensland, and attended Toowoomba Grammar School. A brother and sister survived his death in 1965. He graduated from Sydney University in 1930 and subsequently filled RMO posts at Royal Prince Alfred Hospital (1930-31) and Royal Perth Hospital (1931-32). He became medical superintendent of Fremantle Hospital, WA, 1932-35.

He joined the Public Health Department of Tasmania in 1938, and in 1946 he was appointed medical superintendent of the Tasmanian Chest Hospital. In June, 1950 he became the Assistant Director of Tuberculosis and was appointed Director of Tuberculosis in 1951. He had married Norma Newton in Perth, on 12 July 1933 before the move to Tasmania.

He became Commonwealth Director of Tuberculosis in 1963 in succession to Dr Alan King, and died while still in that position. His death was sudden and quite unexpected. While driving through Ryde with his wife, he collapsed with a heart attack and died. He and his wife had just returned from an international tuberculosis conference in Munich. He was a first- class administrator and extremely popular within the department, with a wide circle of friends and colleagues in Canberra, and throughout Australia. He was a most effective chairman of the National Tuberculosis Advisory Council. They were the heady days of success in tuberculosis control in Australia, carrying on the great initiatives of Harry Wunderly and Hilary Roche. He was survived by his widow, Mrs Norma Tremayne-Brown who subsequently remarried, and their two sons, David and Robin.