The efficacy and safety of oral cibenzoline were evaluated in 42 patients aged 67 +/- 7 (55-80) and with recurrent symptomatic atrial fibrillation for at least a year and for which at least one previous anti-arrhythmic agent had been stopped for inefficacy or intolerance. Cibenzoline was administered for 6 months at the dose of 260 to 390 mg per day in patients aged under 70, with the possibility of reducing this dose in those aged over 70. Clinical, electrocardiographic and 24-hour Holter evaluation took place at inclusion and after 3 and 6 months' treatment or at the time of trial termination for documented recurrence (atrial arrhythmia persisting for 60 seconds or more). The mean duration of atrial fibrillation was 5.6 +/- 5 years (1-26). It was related to ischemic (22%), valvular (17%), hypertensive (17%), hypertrophic (7%) or dilated (7%) heart disease. No etiology was found in 45% of cases. All patients had taken at least one anti-arrhythmic agent in the past (mean of 2 drugs, range 1 to 6). All patients were symptomatic, the commonest symptoms being palpitations (82%), chest pain (28%), feelings of vertigo (11%) or episodes of acute dyspnea (9%). Thirteen patients (31%) had a documented recurrence (> 60 seconds) during the six months of the trial. Recurrence occurred during the first months of treatment in the majority of patients (11 out of 13). The number of symptomatic patients decreased considerably during treatment with cibenzoline, with the disappearance of palpitations in 83% of cases.(ABSTRACT TRUNCATED AT 250 WORDS)