Evidence based medicine and health policy has attained high priority in recent years. This paper considers the role of evidence outside the usual run of evaluations and randomised controlled trials. It considers evidence form history, a discipline that is evidence based by its very nature. The paper considers a number of case studies from the history of drugs, smoking and alcohol policy where research has been demonstrably effective, whether in changing policy or more broadly in changing the way in which the subject is conceptualised by policy makers, the field and the public. It draws out some common themes that seem to have operated historically. It uses these to point to issues that are relevant for today’s moves to bring evidence and policy into a closer relationship.