The description of a new species of Leishmania spp. and the comprehensive study of a yet incompletely understood disease, mucocutaneous leishmaniasis, was a significant accomplishment of the then emerging Brazilian medical and public health science in the early decades of the 20th century. Gaspar Vianna and a group of academic-minded physicians in São Paulo brought forth a task still largely ignored, the complete description of a new nosological entity, in the process forming the core of a parasitological school that would bridge the 20th century with important contributions to medical science and public health. This article analyses the conditions surrounding this group in São Paulo and the major landmarks of their contributions.47335-41