The 2012 Wolfson College Haldane Lecture was given by leading health services researcher Sir Iain Chalmers, currently Coordinator of the James Lind Initiative, Oxford, UK. Sir Iain Chalmers is a leading health services researcher who has spent the past 30 years trying to ensure that health professionals and patients have free access to unbiased evidence of the effects of medical and other treatments. Sir Iain qualified in medicine in the mid-1960s. He practised as a clinician for seven years in the UK and the Gaza Strip, and then became a full time health services researcher with a particular interest in assessing the effects of health care. Between 1978 and 1992 he was founding director of the National Perinatal Epidemiology Unit in Oxford. Between 1992 and 2002 he was founding director of the UK Cochrane Centre, which convened the meeting that inaugurated the Cochrane Collaboration, a not-for-profit, international organization that prepares, maintains and publishes systematic reviews of the effects of health care interventions. Since 2003, he has coordinated the James Lind Initiative to promote public and professional acknowledgement of uncertainties about the effects of healthcare interventions, and research to address these uncertainties.