Transoesophageal left atrial pacing was used to reduce 102 episodes of ectopic atrial rhythms (79 common flutters and 23 ectopic tachycardias) in 83 patients (64 men, 19 women) aged 33 to 85 years (average 61 years). Overdrive pacing, at a faster rate than that of the spontaneous rhythm, was delivered via a bipolar pacing catheter introduced nasally and positioned behind the atrium under fluoroscopic and/or electrocardiographic control. Long pulse durations (up to 20 ms) were used to capture the atria with intensities of less than 20 mA for better tolerance. The overall results were: a) conversion to sinus rhythm in 60.8 p. 100 of cases (47 p. 100 directly and 13.8 p. 100 after transient atrial fibrillation), b) atrial fibrillation lasting over 24 hours in 7.8 p. 100 of cases, c) failure (31.4 p. 100) due to non-capture or intolerance (20.6 p. 100) or recurrence of the arrhythmia after transient atrial fibrillation (10.8 p. 100). Atrial flutter is more accessible to pacing than tachycardia (restoration of sinus rhythm in 63.3 p. 100 and 52.2 p. 100, respectively). Arrhythmias in the postoperative period of cardiac surgery, and isolated and recent arrhythmias were more easily converted. Prior antiarrhythmic therapy did not seem to improve results. Fifty per cent of failures of oesophageal pacing were converted to sinus rhythm by endocavitary pacing. These results show that atrial flutter or tachycardia may be successfully treated by oesophageal pacing in over 50 p. 100 of cases without having to use other forms of electrotherapy (endocavitary pacing or cardioversion).