1 - Based on the experience acquired in the last five years in Bambui, Minas Gerais, where more than six hundred cases of Chagas' disease have been studied, the authors have made a review of the clinical manifestations of this disease. Data on the incidence of schizotrypanosis are reported and the social importance of the disease, which is now being gradually, recognized, is stressed. 2 - The following classification of the clinical forms of the disease is suggested: a) Acute form; b) Chronic forms: 1 - Chronic indeterminate form 9potencial heart disease). 2- Chronic cardiac form (chronic Chagas' heart disease). No nervous manifestations of the kind of those described as the chronic nervous form of schizotrypanosis have been observed in the cases studied in Bambuí. 3 - Clinical and experimental evidences are reported to support the viewpoint that chronic Chagas' heart disease is a well defined clinical entity. 4 - The manifestations of acute infecion are studied in the light of authors' experience with 103 acute cases found in Bambui. Two kinds of edema may occur in patients with acute Chagas' disease: the local edema or edema of portal of entry of the parasite in the organism, and the generalized edema, the so-called "mixedema". The pathogenesis of the last mentioned is reviewed and it is suggested it may be related to hypoproteinemia. The local edema seems to be of inflamatory nature. The manifestations of acute Chagas' heart disease are described. Gallop Rhythm, increase in cardiac shadow (in some cases due to pericardial effusion), prolongation of P-R interval, primary T wave changes and ventricular premature contractions are the more important diagnostic signs of acute Chagas' heart diasease. Right bundle branch block occurred in three fatal cases of acute Chagas' heart disease; in one of them a pronounced ST displacement ("injury pattern") was also present. Death during the acute period of Chagas' disease is usually preceded by convulsions. The manifestations of the acute infection subside spontaneously and gradually in most cases; the disease then goes into the chronic stage and the patients become apparently cured, although still infected. 5 - Patients with chronic infection and without evidences of heart involvement are considered as potencial heart patients and classified in the chronic indeterminate form of the disease. Infection remains in the organism, as a rule under an active form, and signs of heart involvement may devellop later. 6 - Chronic Chagas' heart disease is usually a late manifestation of the infection. About 50% of chonically infected patients present signs of heart involvement. The manifestations of chronic Chagas' heart disease depend upon the severity of myocardial changes. Palpitations, dyspnea, convulsive-syncopal crisis (advanced A-V block) atypical precordial aches and pain in the upper abdominal quadrant (liver congestion0 are the commonest symptoms. Some cases do not present any sumptoms: the heart is not enlarged and the only evidence of myocardial damage is provided by the electrocadiogram (asymptomatic Chagas' heart disease). Irregularities of cardiac rhythm, splintering of second heart sound at the pulmonic area and gallop rhythm are commom auscultatory findings. Heart enlargement involves all the cardiac chambers and is of variable degree. Patients with heart failure usually present pronounced heart enlargement. Signs of cardiac dilatation are predominant over those of cardiac hypertrophy. No signs of valvular deformity or structural changes of the gross vessls are found in this type of heart disease. Blood pressure is normal. Patients with heart failure may present reduced systolic pressure an small pulse pressure. Signs of funcional valvular incompetence are commom in cases with heart failure. Heart failure is usually of right sided type, or is bilateral, being rather uncommon the isolated left sided type of heart failure. In the great majority of cses the electrocardiogram shows disturbances of impulse conduction and/or impulse formation. Ventricular premature contractions, right bundle branch block, A-V blocks of all degrees and atypical alterations of ventricular complexes are the most important electrocardiographic findings. Right bundle branch block is exceedingly common in thos type of heart disease and is of great diagnostic value in endemic areas of schizotrypanosis. Criteria for differential dignosis with other types of chronic heart disease are pointed out. Evolution of chronic Chagas' heart disease is variable, depending chiefly on the activity of infection. Most patients die before 50 years of age. Prognosis depends chiefly on the degree of the enlargement of the heart, on the degree of reduction of the heart's functional capacity, on the type of the existing arrhythmia and on the evolutivity of the infection. Sudden death takes place quite commonly in this type of heart disease but most of the fatal cases die in heart failure. No effective drug is so far available for the etiological treatment of Chagas' disease. Better results are frequently obtained by use of strophantin than with digitalis in the treatment of heart failure of chronic Chagas' heart disease.