The effects on ventricular arrhythmias of a new class IA drug, flecainide, were compared with those of amiodarone in 10 patients with frequent, chronic, and stable ventricular ectopic beats (VEBs). The study consisted of an initial 1-week, placebo-controlled, baseline period followed by two 12-day, randomized, crossover, double-blind treatment periods with incremental dosage and 1 month of placebo between drug periods. Frequent VEBs, which were present in all 10 patients during both placebo control periods (30 or more VEBs/hour every hour, during 24-hour Holter monitoring), were markedly suppressed (reduction greater than 80%) in nine patients with both drugs (p less than 0.01). There was almost total abolition of the VEBs in six patients with flecainide, and the satisfactory results with a minimal dose in three demonstrate its fast onset of action. Side effects from either agent were infrequent and no discontinuation was necessary. We conclude from our study that flecainide is a highly effective antiarrhythmic agent.