A histopathological and immunohistochemical study of the brain and heart was made in 50 patients with the chronic cardiac form of Chagas' disease. The immunohistochemical technique used was the peroxidase-antiperoxidase method adapted for the demonstration of the T. cruzi amastigotes. Histological and immunohistochemical examination of the brain showed encephalitis in multiple foci, although sparse, in four patients (8%). In one of the patients the process was recent, active, and containing parasites. In the other three patients, the lesions were of minor intensity, with light exudative inflammatory changes, suggesting a process becoming inactive, or already inactive. The search for parasites in these three patients was negative, even with use of immunoperoxidase. The heart histological and immunohistochemical study showed, besides the chronic myocarditis in multiple foci associated with interstitial fibrosis, amastigotes in seven patients (14%). The absence of parasites and of inflammatory changes in the brain in the great majority of patients with chronic Chagas' disease, contrasting with the constant finding of inflammatory changes and the occasional finding of amastigotes in the myocardium of the same patients, allows us to state, in the same way other authors did, that there is no histopathological basis to support the existence of the chronic nervous form of Chagas' disease.