The story of leprosy in the Dutch East Indies from the beginning of the 19th century to the middle of the 20th reveals important themes in the colonial enterprise across the territory that is today’s Indonesia. Operating in a territory with only a few hundred Western-trained doctors and a population in the tens of millions, Dutch colonial officials approached leprosy with uncertainty and anxiety. In the early 19th century, the Dutch administration simply removed sufferers from public view: campaigns targetted anyone “looking ugly”. Towards the end of the century, colonial science considered leprosy a hereditary disease of tropical subjects, and therefore undeserving of the colonial government’s limited resources. The leprosariums were emptied. At the start of the 20th century, a growing understanding that leprosy was spread by a bacillus caused a panic that leprosy might spread from the tropics to the colonial metropole. The mixed emotions of pity, fear and revulsion associated with management of the disease intensified, and fed into broader debates on colonial policy. The experts were unsure, and resources were never forthcoming, and despite a view that “bacteria are the same everywhere”, Dutch leprosy treatment in the East Indies mobilized traditional healing practices and relied on home care. Leo van Bergen’s detailed, attentive study to changing policies for treatment and prevention of leprosy (now often called Hansen’s disease) is fascinating medical history, and provides a useful lens for understanding colonialism in Indonesia.