Eighty one patients with ventricular arrhythmias associated with chronic Chagas disease participated in this multi-clinic study. Treatment with Amiodarone and Flecainide were compared using an open, parallel, randomized experimental design. Inclusion criteria required the selected patients to have 1,200 premature ventricular contractions per 24 hours and/or repetitive ventricular arrhythmias. Patients received 60 days of treatment with either Flecainide at 200 to 400 mg per day or Amiodarone 800 to 400 mg per day. This dosage was adjusted to the therapeutic response. Clinical and laboratory evaluations, electrocardiogram and 24 hour Holters were performed at study days: -7, -1, 8/9, 15/16 and 59/60. The percentage reduction of premature ventricular contractions at days 9, 16 and 60 were: 73.1%, 82.9% and 92.4% with Flecainide and 77.6%, 90.1% and 90.7% with Amiodarone. At the end of the study, Flecainide had induced a 92.5% reduction in couplets and 96.5% reduction in ventricular tachycardia. For the same parameters the percentages following Amiodarone were 95.2% and 92.6% respectively. Treatment was discontinued in three patients in the Flecainide group (two because of prolonged sinus node bradycardia and one because of sustained ventricular tachycardia). In the Amiodarone group, treatment was discontinued also in three patients (one because of sustained ventricular tachycardia and two because of severe photosensitive dermatosis). Although there were some differences in the results form center to center, the conclusions from the overall data indicate a similar, therapeutic effect with both drugs.