Most Stories of medical progress come with ready-made heroes. John Snow traced the origins of London's 1854 cholera outbreak to a water pump, leading to the birth of epidemiology. Florence Nightingale's care of soldiers in the Crimean War revolutionized medical hygiene. Yet focusing on individual innovators ignores many of the darker, unacknowledged sources of medical knowledge. Reexamining the foundations of modern medicine, Jim Downs shows that the study of infectious disease depended crucially on the unrecognized contributions of conscripted soldiers, enslaved people, and subjects of empire. From Africa and India to the Americas, plantations, slave ships, and battlefields were the laboratories where physicians came to understand the spread of disease. Boldly argued and urgently relevant, Maladies of Empire gives a long overdue account of the true price of medical progress.