The population surveyed in this study comprised 201 males, 85% of which over 30 years of age. The prevalence of schistasoriasis mansoni was very high (95% positives by the intradermal test, 79% by the hemaglutination test), and at least 28% of the subjects exhibited positive serology for T. cruzi (hemaglutination test). The severity of Chagas' infection, as indicated by an EKG and clinical examination, was found to be very much higher than in some other endemic areas, such as the state of Rio Grande do Sul, and comparable to findings previously reported from Bambuí (State of Minas Gerais): 47% of those with positive serology exhibited électrocardiographic abnormalities, as against 24% of the individuais negative for Chagas' infection. We have also attempted to draw some correlations between serological findings and clinical signs and symptoms. While the area surveyed is included in the control programms run by the Public Health authorities, it has to be stressed that the transmission of trypanosomiasis has not yet been interrupted. The authors were unable to prove that the concomittance of Chagas' infection and schistosomiazis mansoni leads to the same grave clinical patterns as observed in experimental animals.