Flecainide is a Class I antiarrhythmic drug of the local anaesthetic type. It can be given either intravenously or orally and its pharmacokinetic properties allow relatively long (12 hours) dosing intervals with oral administration. In several open and a few controlled therapeutic trials, orally administered flecainide has brought about a greater than 90% suppression of ventricular ectopic beats in about 80% of patients. A similar percentage of patients (83%) experienced at least an 80% suppression of their ventricular tachycardia in these trials. A slightly greater response rate was reported with intravenous infusion of flecainide. Initial results in arrhythmias complicating the Wolff-Parkinson-White syndrome have been favourable. Comparative trials are few in number but flecainide has proved to be more effective than quinidine, and possibly more effective than disopyramide, mexiletine, tocainide and propafenone, in suppressing ventricular ectopic activity. The most commonly reported extracardiac adverse effects have been dizziness and visual disturbances. Proarrhythmic effects have been reported in 7 to 8% of patients, with a higher incidence in patients with serious ventricular tachycardia and reduced myocardial function. The moderate negative inotropic effects of flecainide can become clinically significant in patients with impaired ventricular function. Thus flecainide, with its convenient dose schedule and apparently low incidence of serious side effects, would appear to be a useful addition to the antiarrhythmic agents available. Further studies are needed though, to confirm its long term tolerability when used prophylactically.