This study examines the constructions of leprosy in Colombia from the late nineteenth century to the 1930s. In the nineteenth century Colombian physicians constructed leprosy as highly infectious and threatening and adopted rigid segregation of “lepers” to prevent its propagation. At the same time, medicine was becoming a profession in Colombia, and physicians used leprosy to build their cultural and scientific authority. In order to assert their power, doctors exaggerated the number of leprosy sufferers, and unfolded a nationalist rhetoric. Colombian isolation policies had their roots in Spanish medieval traditions and in international examples. Colombian physicians were aware of European scientific developments. In the 1870s, the Norwegian physician Gerhard A. Hansen postulated what later came to be known as Mycobacterium leprae as the causative agent of leprosy. In 1897, the first international conference on leprosy declared leprosy a disease produced by Hansen’s bacillus. Meanwhile, Westerners discovered leprosy in their colonial territories during their imperialist expansion of the late nineteenth century. They developed a racialist image of leprosy as a disease afflicting inferior peoples, and instituted an international movement to build leprosaria in which to isolate patients. Colombian doctors also adopted a colonialist attitude towards their own leprous population. In the early twentieth century, the Colombian government, took charge of leprosaria, imposing severe regulations related to compulsory isolation. The state and the physicians treated leprosy as a disease apart, reinforcing prejudices of medieval origin. They tried to transform the town-lazarettos, which had been built by patients themselves in the 1870s, into colonies exclusively for lepers. Patients actively resisted the medicalization of leprosy, and non-leprous people remained within the lazarettos during this period. In the 1930s, the medical rhetoric started to change. As a result of improvements in leprosy therapy, doctors began to regard leprosy as a curable disease and to reject compulsory isolation for patients in all stages of infection. The physicians’ emphasis shifted from isolation to prevention and research. Scientific prevailed over social reform, and physicians and the government gave priority to searching for a vaccine instead of improving the general living conditions of the population. / Ph. D.