Walter Mercer was born on 19 March 1890 at Stow, Midlothian, where his family owned the local tweed mills. He went to school at George Watson's College, Edinburgh, and in 1907 began the study of medicine in the University of Edinburgh, with which he was to be associated for almost the whole of the rest of his life. He graduated MB ChB in 1912, and after house posts in Carlisle and Edinburgh he joined the RAMC and served as regimental medical officer in the King's Own Scottish Borderers and the Royal Scots Fusiliers in France, Italy and the Mediterranean. Being invalided home, he became attached to the Edinburgh War Hospital at Bangour where his special interest in orthopaedics may be said to have started. After demobilization in 1920 he was appointed surgeon in charge of Tynecastle Orthopaedic Clinic under the Ministry of Pensions, and in 1921 he obtained the FRCS Ed. In 1925 he joined the staff of the Edinburgh Royal Infirmary, and as a member of the Professorial Unit was alloted the care of orthopaedic cases and fractures. But at the same time he undertook the duties of a thoracic surgeon at the South Eastern Counties of Scotland Sanatorium at East Fortune, and although he will long be remembered for his technical dexterity and the advances he made in orthopaedic surgery, he continued the practice of abdominal and cardiac and pulmonary surgery till 1948. During the second world war Mercer was appointed consultant in orthopaedic surgery to the Department of Health, and surgeon to the thoracic unit for the East of Scotland; but in 1948 he became the first holder of the Law Chair of Orthopaedic Surgery in the University of Edinburgh, in which he continued till his retirement in 1958 when he was made Emeritus Professor. During that 10 year period he devoted himself entirely to the development of the practice and teaching of orthopaedics in the University. His well-known textbook of orthopaedic surgery first published in 1923 was later extended into six editions and several translations. He was Vice-President of the British Orthopaedic Association, and Chairman of the Editorial Board of the *Journal of bone and joint surgery*. Walter Mercer made considerable contributions to the Royal College of Surgeons of Edinburgh, and was President from 1951 till 1956, during which time many advances were made in the College's educational activities. The Surgical Colleges of England, America, Canada, and South Africa conferred on him Honorary Fellowships, and the University of Liverpool awarded him the Honorary degree of MCh in orthopaedics. A knighthood was conferred on him in 1956. This wonderfully versatile man had many interests outside his professional work, and was a charming and friendly host. In his earlier years he was a keen tennis player, a good shot, and a modest golfer, and in later life an enthusiastic philatelist. In 1928 he married Helen Maisie Lunan who had played with him in many Scottish tennis tournaments, and they took great pleasure in entertaining his assistants and the numbers of friends who visited them from near and far. When "Wattie" died on 23 February 1971 at the age of 80, his wife and their son David survived him.