His great grandfather migrated from Scotland to Ballarat in 1859 during the gold rush and opened a printers business which was to remain in the family for three generations. But William Bowie did not follow his father's occupation. He matriculated from Ballarat High School with a scholarship to Ormond College and so began his medical career. He completed his course in 1952 with honours in all his final year subjects and after a year as resident at the Royal Melbourne Hospital served in the RAAF at Moratai in the Mollucas as medical officer to the 79th Squadron whose pilots were then flying spitfires. On his return in 1945 he was employed by the Royal Melbourne Hospital for a year and then spent 1946 as a resident and registrar at the Royal Children's. He believed in the value of a period in general practice as part of a doctor's training and worked as an assistant to a practice in Hobart before returning to the Royal Children's where he remained until 1952 spending part of his time as an associate in Howard Williams' clinical research unit.

Bill was noted for his ability to focus his mind on what he was doing to the exclusion to all external distraction and it is said at the Children's Hospital that when he was studying for his MD and College membership in 1950, a rat entered his room and died. Soon the smell was noticed by visitors and eventually even by passers by, but not by Bill. No one commented because his powers of concentration were legendary and it was at first assumed that the attention he was giving to his studies was so great that it was leading him to neglect his person. This ability to devote his entire attention to what he was doing ignoring all else caused his colleagues to admire him but also to regard him with a kind of amused exasperation. Bill used to claim that he never wore a watch and Peter (later Sir Peter) Tizard, then Professor of Paediatrics at Hammersmith and Oxford, once said that he always took any letter from Bill to bed with him knowing that although it might be of importance he would probably fall asleep before he had finished reading it.

While in Melbourne Bill met Judith Henzell, the daughter of Linley Henzell Commissioner of Public Health in Western Australia, who was studying medicine at Melbourne University, there being no medical school in Perth at that time. They were married in 1954 and had a daughter and three sons. The oldest son 'Will' followed his father obtaining his FRACP in 1989 and working in paediatric research. In 1954 WB Macdonald was awarded a Nuffield Travelling Scholarship and worked in Dr Lightwood's Department at St Mary's Hospital in London where in 1955 he was appointed lecturer in paediatrics. His scientific publications while with Lightwood were mainly about the rarer disorders of fluid and electrolyte metabolism two of which Lightwood had been the first to describe and one of which (Lightwood's syndrome) bore his name. In 1958 he was offered the chair of child health in Perth. The people of Western Australia who had contributed more than a million pounds, a large sum at that time, to found a new medical school, were intensely proud of it and perhaps had at first unrealistic expectations as to what it might achieve and so on his arrival in Perth the new professor was subject to great pressures to chair meetings, to address community groups, to give public lectures and to express opinions about child health welfare and education. Because of these demands and because at that time facilities were limited he made the decision to concentrate on graduate and undergraduate teaching.

In 1964, supported by the New York Commonwealth Travel Fund he spent a year as lecturer in paediatrics at Harvard Medical School and the Boston Children's Medical Centre with Dr Janeway. During the sixties he carried out a number of assignments as consultant for WHO visiting India, Sri Lanka, Thailand, Burma and Fiji, and at one time was part of an advisory panel on maternal and child health for WHO. This was work he particularly enjoyed. He liked travelling. He readily achieved rapport with health authorities and politicians in the countries he visited and he never seemed vulnerable to the debilitating infections which so often afflict Westerners travelling in Asia. He was a keen photographer and his camera accompanied him on his travels. Despite his achievements and his involvement with people in many different organisations there was a simplicity almost and innocence about him which disarmed those he met whether they were patients or politicians from the third world. As time passed he continued to publish but his topics were now undergraduate or graduate education and the social problems of Australian children.

His chairmanships, fellowships, memberships and consultancies included appointments at Princess Margaret and King Edward Memorial Hospitals, the Royal Australasian College of Physicians, the Australian College of Paediatrics, the National Health and Medical Research Council, the World Health Organisation, the Australian Medical Congress as president, the Australian Post Graduate Federation in Medicine, the Australian Medical Association study group on medical education, the Preschool Commission, the Telethon Foundation and much more. He received strong support from Ian Lewis who afterwards became professor of child health in Hobart. As a councillor of St Columba's College he contributed much and he was a member of a committee of Clan Donald responsible for the restoration of Armadale. He was a keen follower of Australian football and supported Subiaco often attending games with Dick Joske, professor of medicine.

In 1976 he had an illness which was diagnosed as non-Hodgkins lymphoma. Treatment was at first effective and he had a number of remissions being well for four of the next seven years until his final illness in 1983. Among his qualities was an understanding of the needs and feelings of the medical students who elected him year after year as patron of their society. They had arranged a presentation to show their admiration for him and their appreciation of his support over the years but he did not survive to receive it and it was presented to his widow Judy. It bore the inscription:

W B Macdonald ... Patron of the W A Medical Students' Association 1957-1983 with affection and gratitude for an outstanding contribution to a generation of medical students.

There is now a travelling scholarship awarded annually to a fifth year medical student and an annual oration in his memory. The WB Macdonald Lecture Theatre at Princess Margaret Hospital is named after him.