MB BS Lond 1956, MD 1967; FRCP Edin 1980; FRCPath 1978.
Maclaren was born in Ellon, Aberdeenshire on 21 December 1928. He trained at the University of Aberdeen and at Guy's Hospital where he was house officer and lecturer in bacteriology. In 1964, Maclaren became consultant pathologist to Stockport and Buxton Hospital Group, a position he held for at least ten years. He later went to Amsterdam where he was professor in clinical bacteriology at the Free University.