In the context of an open multicentre study, 593 patients participated in the evaluation of sustained release disopyramide (*) in the treatment of cardiac arrhythmias. One hundred and seventy one (29%) had a ventricular arrhythmia, 382 (64%) a supraventricular arrhythmia and 40 (7%) an atrial and ventricular arrhythmia. Two hundred and seventy patients (46%) had underlying cardiac disease. Disopyramide was administered at the mean daily dose of 462 +/- 95 mg. The effectiveness of treatment was assessed after 3 and 6 months by Holter in the group treated for ventricular arrhythmias, the responder rate was 52.6% at three months and 58.1% at 6 months. It was significantly (p < 0.001) greater in the group treated for supraventricular arrhythmias (71.3% at 3 months and 82.1% at 6 months). The Holter responder rate in patients aged over 65 (70.5% at 6 months) was high and general and cardiac acceptability similar to that in younger patients. Adverse events led to the interruption of treatment in 8.2% of patients. Thus the effectiveness/acceptability ratio of SR disopyramide makes it entirely appropriate for the treatment of cardiac arrhythmias, even in the elderly.