In this multicenter trial, the efficacy and safety of flecainide, a new antiarrhythmic agent, were compared with those of quinidine, a standard antiarrhythmic agent in the United States. A randomized, parallel, placebo-controlled design was used. Flecainide was more effective than quinidine (p < 0.0001) in reducing ventricular premature complexes, couplets and ventricular tachycardia. Flecainide continued to be effective in reducing ventricular arrhythmias during a 12-month follow-up period. The incidence of side effects was similar for the 2 drugs in both short- and long-term studies. Therefore, flecainide should be an excellent drug to use in treating patients with ventricular arrhythmias classified as either benign or potentially malignant.