The study of the cerebellums of 12 patients with chronic Chagas' disease (chronic chagasic cardiopathy) has shown numeric reduction of the Purkinje cells with regressive changes in the remaining ones, changes in the nervous fibers of the Purkinje's cells nests and microgial mobilization. The same alterations were found in the cerebellums of 9 patients with non chagasic cardiopathy but, like the chagasic ones, with congestive heart failure. Two cerebelleums of "normal" persons accidentally died were used as controls. The changes in the cerebellar parenchyma were considered as resulting from hypoxaemia of the central nervous system due to congestive heart failure.