Bloodletting by phlebotomy has been an obsession with medical practitioners for thousands of years, causing countless suffering to patients, initially for unproven indications and more recently for diagnoses. The approach to medical evidence-based phlebotomy has been a triumph for scientifically inclined practitioners. Progress, primarily achieved since the nineteenth century, has been in spite of considerable opposition from the medical establishment. The evaluation of phlebotomy as a useful tool continues and no doubt further myths will be dispelled. The history of bloodletting remains one of the greatest stories of medical progress, not because of new discoveries but mainly by persistent unbiased audit.