Born on 17 August 1898 second child and only son of John Bathgate Johnston, merchant, and Lilian May his wife, he was educated at Adelaide High School and University, qualifying in 1924. He came to the London Hospital and, after two years postgraduate study in England, returned to South Australia, where he was medical officer to Port Pirie Hospital from 1928 to 1946, living at Lauriston, Balmoral Road, Port Pirie. He was clinical assistant in the surgical section of the Royal Adelaide Hospital 1946-52, and practised at Liberal Club Buildings, North Terrace, Adelaide. He married in 1935 Lilian Davies, who survived him with two sons, and died on 12 March 1952 at 105 Prospect Road, Prospect, SA.