Jim Downs has written an ambitious book that traces the unique ways imperial medicine shaped modern medicine, particularly epidemiology. The book has two main aims. First, Downs shows that colonialism created specific environments, particularly confined spaces such as military hospitals, ships, and plantations, which provided ideal conditions for the detailed observation of the spread of diseases and the conduct of controlled medical experiments and vaccinations. In doing so, he challenges the conventional approaches to the social history of medicine that focus mainly on Europe and maintain an uneasy relationship with its colonial counterpart. Its second aim is to shift the focus of the history of medicine “from medical authorities to the people who made their theories visible” (200). Downs seeks to recover the lost voices of slaves and colonized people subjected to medical experiments. The book is evidently successful in refocusing the history of epidemiology on empire, but less so in uncovering lost voices. We do not hear the voices of the slaves, hajj pilgrims, or those confined to army barracks or ships. The narrative is based primarily on the familiar study of white colonial actors such as Arthur Holroyd, James O. McWilliam, and Florence Nightingale.