International health organizations emerged in the 19th century as a means to reconcile the needs of a world of increasing trade and mobility with the increasing threat of the spread of diseases. Inexorably, they have assumed a growing list of responsibilities. Throughout the 20th century, their work has been torn between two approaches to health: one biomedical, which saw health as a function of pathogens and diseases and called for vertical campaigns against specific diseases, another social, which considered diseases mere symptoms of underlying problems of poverty and inequality and which favored horizontal programs of social change. Inevitably, the activities of international health organizations like the Rockefeller Foundation, the League of Nations Health Organisation, the World Health Organization, the World Bank, and others have maneuvered between those positions. The international eradication campaigns against malaria (unsuccessful) and smallpox (successful) and the principles adopted at the Conference of Alma-Ata stand out as pivotal examples of biomedical and social approaches to health in the post-WWII period. Implicitly, international health organizations have provided a mirror image of how those in power, the community of nations and – eventually – all citizens and voters, have decided to organize their interaction with their biological environments, their material and immaterial resources, their political priorities, and with each other.