We report two cases of Chagas' disease with megacolon who presented with chronic diarrhea. One of the patients also had evidence of malabsorption, such as steatorrhea and hypocalcemia. Barium meal follow-through showed remarkable dilation of the jejunum in both cases and, in one of them, an associated megaduodenum. Manometric studies of gastrointestinal motility showed abnormally slow propagation of the interdigestive migrating motor complex, which was also excessively prolonged. Cultivation of jejunal aspirates revealed strict anaerobic bacterial growth in both cases. Oral antibiotic therapy led to substantial improvement in symptoms. The two cases herein reported indicate that clinical manifestations of small bowel bacterial overgrowth, possibly caused by motor disturbances associated with megajejunum, may occasionally include the clinical picture of gastrointestinal involvement in Chagas' disease.