Tropical medicine is normally said to date from the late nineteenth century, being particularly associated with the work of Patrick Manson. Like other pioneers of the discipline, Manson broke with previous ideas about diseases in the tropics which stressed the role of climate in their production. The new scientific discipline of tropical medicine was based on the discovery that most diseases in the tropics were caused by microbial pathogens, some of which were transmitted by arthropod vectors. Despite this, and the fact that Manson and others recognized that most so-called tropical diseases were not confined to the tropics, the term ‘tropical’ was retained. This chapter explains why that was so, looking back to ‘tropical medicine’ before Manson and afterwards at the development of a new discipline, created in order to assist colonial development. The chapter examines how tropical medicine changed from being exclusively about protecting imperialists and their investments to a discipline that was increasingly owned by the peoples of tropical countries.