Prof. Leong was brought up in Hong Kong and then went to attend McGill University in Montreal Canada. He did Honours Biochemistry as an undergraduate, and then Medical School. Further postgraduate training in Obstetrics and Gynecology followed, and he obtained his specialists degree in 1974. He then went to London on a McLaughlin Fellowship granted by the Canadian Royal College where he studied under Professors Richard Beard and Stuart Campbell. Returning to Montreal, he joined the McGill University Department as academic staff, and was active in teaching and also headed the High-Risk Obstetric Unit. In 1979 Prof. Leong returned to Hong Kong and engaged in private practice. He then set up the IVF Centre at the Hong Kong Sanatorium and Hospital, which then became one of the most successful IVF clinics in Asia and the world.