BACKGROUND AND OBJECTIVES: Atrial fibrillation(AF) is the most frequently encountered arrhythmia in clinical practice. Pharmacologic therapy has been advocated for both immediate restoration of sinus rhythm and prevention of recurrent AF. Because conventional antiarrhythmic therapy is often ineffective in maintaining sinus rhythm or is associated with adverse side effects in patients with AF, recent interest has focused on the use of class III antiarrhythmic agents. This study investigated the efficacy and safety of sotalol and amiodarone for conversion of chronic AF and prevention of recurrent AF. MATERIALS AND METHOD: Thirty six patients with AF were firstly received sotalol by prospective study protocol. The patients were classified as having paroxysmal AF(PAF, N=2) or chronic AF(CAF, N=4) based on AF pattern. If the patients with CAF did not convert to sinus rhythm or the patients with PAF recurred in AF, the patients were received second agents(amiodarone). Patients were followed up for one year. RESULTS: Among the 12 patients with PAF receiving sotalol, 10(83.3%) patients remained in normal sinus rhythm for average 9.4+/-3.6 months. Sotalol was replaced by amiodarone in the remaing 2 patients with arrhythmia recurrence and 1 of the 2 patients remained in sinus rhythm during the follow-up period. In the case of 24 patients with CAF, conversion to sinus rhythm was achieved in 5(20.8%) patients with sotalol. Among the patients with CAF who were not respond to sotalol, 17 patients received amiodarone subsquently and 3 patients successfully converted to sinus rhythm. There were no proarrhythmic effects related to both agents during the study period. CONCLUSION: Both sotalol and amiodarone appear to be less effective in the termination of CAF, but sequential use of these two agents seem to be very effective for the prevention of recurrence of PAF.