The undetermined form of Chagas' disease is diagnosed in asymptomatic subjects with a positive blood test for Chagas' disease, normal resting electrocardiogram, chest X-ray, barium esophageal and large bowel radiological studies. Other investigation methods are not recommended for identification of other organs damage lesions in this phase of the disease. When other methods of investigation were employed, cardiac and digestive abnormalities of small magnitude were detected without prognostic implications. These findings do not warrant frequent examinations of patients with undetermined form of the disease except for the electrocardiogram or if the patients report other clinical manifestations. The benign course of the disease does not preclude ability to work and the subjects should be considered apt for work in any profession.