Mark Elwood studied medicine in the UK and epidemiology and public health in the US and Canada. He has been a Professor of epidemiology in Nottingham, England, Vancouver, Canada, Melbourne, Australia, and Dunedin and Auckland in New Zealand. His contributions have been in cancer aetiology, prevention and early diagnosis, but include studies of birth defects, health care outcomes, and many clinical topics. He first produced this text in 1988 and has used it and its developments in teaching his evidence based approach to clinical appraisal to health practitioners, health managers, and postgraduate and undergraduate students.