Cannabis has been the subject of much policy and media attention in the last few years and the 2004 legal changes under the Misuse of Drugs Act in the UK, were widely, although incorrectly, presented as liberalization or legalization of the drug. Current debates over the classification of cannabis as Class C or B serve to emphasize the controversies that surround the drug. This paper provides an overview of a Wellcome Trust three-year project that is currently in progress. Framed as a history of science and policy making, the project aims to study the process whereby boundaries shift between illicit 'drug' and licit 'medicine' and the issues and interests that are involved in that transaction. Specifically, the project aims to analyse the trajectory of research since the 1950s, the interests involved, in particular the role of scientific research and allied professions; industry; drug technology; and lay knowledge and user activism. It aims to analyse the interaction of science and medicine with policy through the examination of the policy role of expert committees and their membership. The impact of international agencies will also be considered. Lastly, it will assess the overall impact of medicalization on the policy environment. Standard historical methodology will be applied and a wide variety of published and archival source material, as well as semi-structured oral history interviews, will be utilized. © 2008 Informa UK Ltd.