The article presents the ethnographic approach to two towns that were lazarettos for the separation of people affected with leprosy during much of the nineteenth and twentieth centuries. It focuses on the experiential knowledge of leprosy that controverts biomedical definitions. In that dissent it becomes apparent a problematic medicalization of the disease, which is intelligible to the light of a tradition of resistance to the segregation that has been historically imposed on the populations that were once lazarettos.