Born 1 May 1885 in London, son of Sir Thomas Mackenzie, High Commissioner for New Zealand and a former Prime Minister of the Dominion, and Ida Nantes, his wife. He was educated at the City of London School and in New Zealand at Balclutha, Robin Hood Bay and Otago Boys' High School, and after a year at Otago University went to Edin-burgh where he graduated in 1908, proceeding MD 1911 with a gold medal, and winning the Gunning Victoria jubilee prize for this thesis on pituitary gland function. He took the English Fellowship in 1912 and the Edinburgh MCh in 1913. Returning to New Zealand he settled in practice at Auckland, and was appointed surgeon to the Auckland Hospital in 1914. During the war he served with the New Zealand Medical Corps. After the war he inaugurated clinical teaching in the hospital and continued to lecture till his death. He had been examiner in physiology at Otago University from 1914 to 1916, and was examiner in gynaecology 1926-28. He was a member of council of Auckland University College 1921-35 and president 1933-35, and for several years a senator of the University of New Zealand. He was an excellent teacher, and did much to improve medical education in New Zealand. In 1923 he founded the Auckland Clinical Society, of which he was president in 1924. He was at one time president of the British Empire Cancer Campaign in New Zealand, and was president of the Auckland branch of the British Medical Association in 1929 and a member of the editorial committee of the *New Zealand Medical Journal* (BMA). He was a charter member of the Auckland Rotary Club and its president 1924-5; and an honorary serving brother of the Order of St John of Jerusalem. Mackenzie was an accomplished general surgeon, with a special interest in gynaecological surgery. He kept elaborate and carefully analysed notes, and was a frequent contributor to professional congresses and journals. He married on 28 April 1913 Flora Honor Macdonald, who survived him with a son and three daughters. His younger brother, Hector Bruce Mackenzie, MB, practised as a radiologist at Auckland, and died there in 1950. He practised at 27 Princes Street, Auckland, and had a country place in the forest, high in the Waitakere mountains. He died at Auckland on 15 January 1942 after three weeks' illness, aged 57. Publications:- An experimental investigation of the mechanism of milk secretion. *Quart J exper Physiol* 1911, 4, 305. The repair of large abdominal herniae by muscle transplantation. *Brit J Surg* 1924, 12, 28. Hyperadrenalism. *Aust NZ J Surg* 1937, 7, 175. Hyperparathyroidism. *Ibid* p 256.