One hundred consecutive patients admitted in 1980-82 for direct current conversion of chronic atrial fibrillation (AF) were followed. The first attempt to convert was made without the institution of class I antiarrhythmics. If AF relapsed, patients were selected for further conversions, in connection with which quinidine or disopyramide treatment was instituted. The proportion of patients maintaining sinus rhythm (SR) one and two years after the first conversion was 23% and 16%, after the second conversion 40% and 33% and after any number of conversions [1-12] 54% and 41%. Fifty-three per cent of the patients were symptomless before at least one conversion. Of the patients maintaining SR two years after conversion, 46% did not receive antiarrhythmic therapy. More than two conversions should be exceptional since symptoms of AF are often absent and the additional effect of further conversions is minor. A first attempt to convert without antiarrhythmics identifies a substantial proportion of patients maintaining SR without any prophylactic antiarrhythmic therapy.