Dr. Barr was born in Scotland and graduated from the Faculty of Medicine at the University of Glasgow. Following training in internal medicine and haematology he joined the team from Glasgow at the University of Nairobi, contributing to the establishment of the first Faculty of Medicine in Kenya. From 1974-1976 he was a Visiting Scientist at the National Cancer Institute (NCI) in the US which allowed him to complete his doctoral thesis on Human Haematopoietic Homeostasis. In 1977 he joined the Department of Pediatrics at McMaster University where he was head of the Division of Hematology and Oncology from 1981-2008. Dr. Barr collaborated with Dr. Archie Bleyer in developing adolescent and young adult (AYA) oncology in the Children’s Oncology Group from 2000 and the NCI from 2005, then co-chaired the Canadian National Task Force on AYA Oncology, headquartered at McMaster, which operated from 2008-2016. Recognition of his accomplishments led to the award of the O. Harold Warwick Prize for Cancer Control Research from the Canadian Cancer Society in 2009. In November 2020 Dr. Barr was appointed to the Order of Canada.