Interest in medicinal plants has increased in recent years. This article examines the history of medicinal plant research through a case study of the London School of Hygiene and Tropical Medicine (LSHTM) over the past 100 years. Papers published by members of the School and documents in the School archives show a fluctuating but continuous interest in plants as sources of medicine. Research interests of individual scientists, changes in the School structure and the changing role of research affected research into medicinal plants at LSHTM. As important were external developments, including the supply of plant resources, especially during wartime, the development of drug-resistance, advances in science and technology, knowledge exchange between both disciplines and cultures, the increased influence of global organizations on policy, as well as pressure groups particularly those involved in conservation. With the revival of interest in plants and the increasing variety of influences on research, it is important to have a better understanding of how debates and subsequent policy impact at the research level, and how research in turn impacts upon policy.