The aim of this study was to determine the prevalence of stroke in a hospital-derived cohort of patients with chronic Chagas' disease. Seventy-nine patients with chronic Chagas' disease were prospectively followed at the Cardiomyopathy Clinic of the Santa Casa Hospital from January 1990 to June 1993 (mean follow up = 17 +/- 12 months). Mean New York Heart Association functional class was 2.42 +/- 1.24. Fifty-six (70%) patients were on angiotensin-converting enzyme inhibitors at maximum tolerated doses, but no patient was on anticoagulation therapy. Atrial fibrillation was detected on the resting ECG in twelve (15%) patients. On echocardiography, mean left ventricular ejection fraction was 49.07 +/- 17.96% and mean left ventricular diastolic dimension 60.12 +/- 10.97 mm; mitral regurgitation was detected in 20 (29%) patients. Left ventricular thrombus was seen in three (4%) patients; all of them were in sinus rhythm and had left ventricular dysfunction on echocardiography. No thromboembolic event, however, was detected during the follow-up. One patient (1%) had a fatal stroke during the study period; she was in sinus rhythm on the resting ECG, and had mild mitral regurgitation, normal left ventricular function and no intracavitary thrombus on Doppler echocardiography. The prevalence of stroke is low in a hospital-derived cohort of patients with mild to moderate heart failure due to chronic Chagas' disease. Routine prophylactic anticoagulation, therefore, seems not to be warranted.