Born at Rochester, Minnesota, 28 July 1898, son of Charles Horace Mayo and his wife Edith Graham. After leaving Princeton he studied medicine at the University of Pennsylvania, graduating in 1927, when he joined the Mayo Foundation as a Fellow in Surgery, the fourth member of that remarkable family whose name is forever commemorated in the Mayo Clinic. He was appointed consultant surgeon in 1931, became Professor of Surgery in 1948, and served on the Board of Governors from 1933 until his retirement in 1964, when he was appointed Emeritus Professor. Mayo's work in the field of abdominal surgery was universally recognised and he received honours from many overseas countries as well as in his own. During the second world war he served in the Medical Corps of the US Army, becoming Commanding Officer of 237th Station Hospital, New Guinea. He was a founder of the American Board of Surgery. He had many interests besides surgery and was regarded as an excellent ambassador for his country, representing the United States of America on several important overseas missions. He was the US delegate to World Health assemblies, and President of the American Association for the United Nations. Charles Mayo and his wife Alice Varney Plank, whom he married in 1927, were well-known for their generous hospitality to visiting surgeons, especially those from Britain, and during the time of the threatened invasion of England in 1940 they opened their home to several British families and cared for them as for their own. They had four sons, one a doctor, and two daughters, and brought up the two sons of his brother Dr Joseph Mayo who had died at the age of 34. Mrs Mayo died on 9 November 1967, and Charles Mayo was killed in a car accident on his seventieth birthday, 28 July 1968. There is a portrait-photograph taken in 1958 in the Honorary Fellows' album in the College Library.