Background Long-term maintenance of sinus rhythm after successful conversion of chronic atrial fibrillation (CAF), often ameliorates patients symptoms, reduces the risk of ischemic stroke and improves cardiovascular hemodynamics. This prospective study aims to evaluate the long-term efficacy and safety of very low-dose amiodarone (100 mg daily) for the maintenance of sinus rhythm after successful direct-current (DC)cardioversion in patients with CAF and rheumatic heart disease (RHD) post intervention.Methods This study was a randomized prospective trial. One day after successful DC cardioversion (remained normal sinus rhythm) in patients with CAF and RHD post intervention for more than six months and adequate anticoagulation, all were randomly administered either amiodarone 200 mg daily in group A or amiodarone 100mg daily in group B.Results A total of 76 patients (40 men and 36 women) were examined from February 1998 to December 1999.The mean age of the patients was (66±10) years, and the mean follow-up was (67±8) months (range 61 to 84months). Actuarial rates of the maintenance of sinus rhythm were similar in the two groups after 5 years of follow-up. Four patients (11%) in group A but none in group B experienced significant adverse effects that necessitated withdrawal of amiodarone. No death occurred during the study period.Conclusion A very low dose of amiodarone results in adequate long-term efficacy and is safe for maintaining sinus rhythm in patients with CAF and RHD post intervention after successful DC cardioversion.