During the last 8 years 58 acute cases of Chagas' disease were studied. Patients from an endemic area of the state of Barinas, Venezuela, showed fever (98%) and circulating forms of T. cruzi (100%), and were treated with oral benznidazole. The recorded mortality was 8.6%. Acute myocarditis was constantly found either in myocardial biopsies or at necropsy, even in patients without any other sign of cardiac compromise (36%), which was detected by chest X-ray in 58%, by 2D echocardiography in 52%, by resting ECG in 41% and by clinical findings in 27.5% of the patients. Cardiomegaly was due to pericardial effusion rather than ventricular dilatation in most instances. Treatment eliminated parasitemia but negativized serology in only 20% of patients. It also appeared to have little influence on the ongoing myocarditic process, emphasizing the need for better therapeutic schedules, able to avoid or control the early appearance of immunologic mechanisms and microcirculatory damage involved in the future development of chronic chagasic myocarditis.