One hundred and sixty-nine patients with a wide range of cardiac arrhythmias and who had been treated with chronic oral flecainide acetate were reviewed retrospectively. The most common arrhythmia was atrial fibrillation (32%), and 20% of the patient population had the Wolff-Parkinson-White syndrome. Five hundred and three treatment episodes were assessed, 254 with flecainide alone or in combination, mean duration 7.3 +/- 9.4 months, and 249 without flecainide, mean duration 9.5 +/- 12.3 months. The most common dose for flecainide was 200 mg/day (57% of episodes), and it was used alone in 82% of flecainide treatment episodes. Arrhythmia frequency was reduced or abolished in 73% of flecainide treatment episodes, with little difference between arrhythmia groups. Unwanted effects were seen in 14% of flecainide treatment episodes, and half of these cases were managed by dose adjustment. It is concluded that flecainide acetate is effective in a wide range of cardiac arrhythmias, and that long-term management problems are few.