Environmental historians are not sufficiently aware of the extent to which mid twentieth-century thinkers turned to medical geography—originally a nineteenth-century area of study—in order to think through ideas of ecology, environment, and historical reasoning. This article outlines how the French–Croatian Mirko D. Grmek (Krapina, 1924–Paris, 2000), a major thinker of his generation in the history of medicine, used those ideas in his studies of historical epidemiology. During the 1960s, Grmek attempted to provide, in the context of the Annales School’s research program under the leadership of Fernand Braudel, a new theoretical framework for a world history of disease. Its development was inspired by several sources, most notably the French...