A case of chronic Chagas disease, associated with chronic lymphocitic leukemia is reported. Acute manifestations of Chagas disease, characterized by acute encephalitis, with demonstration of Leishmaniae in the central nervous system were observed. This aspect is unique in the literature, since Chagas encephalitis appears only as a manifestation of the acute form of the disease, and not as a complication of the chronic form. The fact is interpreted, in this case, as secondary to alteration of the immune state, due to the presence of chronic lymphocitic leukemia.