In the "Blood Bank" of the Hospital do Pronto Socorro in Belo Horizonte, Minas Gerais, Brazil, 576 individuals were submitted to the routine medical examination which is required before applicants are accepted as regular blood donors. Among the blood tests which were performed, it was included, this time, the complement-fixation test for CHAGAS' disease, the antigen being prepared from cultures of S. cruzi. Fourteen individuals showed positive reaction for CHAGAS' disease. Of these, 7 were submitted to xenodiagnosis, to electrocardiographic examination and to X-rays examination of the heart and of the basal vessels. All of the 7 individuals have lived in huts which harbored triatomid-bugs, in regions where CHAGAS' disease is endemic. The electrocardiograms showed myocardial lesions in 3 cases: two of them had right bundle-branch block, and one presented complete A-V block. The xenodiagnosis showed that 3 out of the 7 individuals with positive complement-fixation test had S. cruzi in their blood. After discussing the problems allied to the transmissibility of CHAGAS' disease by blood transfusion, it was stressed the necessity of including the complement-fixation test for schizotrypanosis among the tests required from prospective blood donors.