Background and aim: We reported that the low level of plasma B-type natriuretic peptide (BNP) may help to predict the short-term (4-week) maintenance of sinus rhythm after electrical cardioversion in atrial fibrillation (AF) patients. However, there have been no conclusive data whether the BNP level is associated with long-term maintenance of sinus rhythm after the procedure. Therefore, we studied the association of the BNP level and AF recurrence in a short- and long-term period. Methods: We recruited, in a prospective way, 26 consecutive patients with persistent AF without symptomatic congestive heart failure. Plasma BNP were measured before and after electrical cardioversion. Recurrence of AF was monitored in 1-week and 1-, 3- and 12-month. Results: AF was converted to sinus rhythm in 24 among 26 patients (92.3%) after the procedure. Maintenance of sinus rhythm was found in 75.0% in 1 week, 56.5% in 1 month, 66.7% in 3 months, and 66.7% in 12 months. The BNP levels significantly decreased after cardioversion in all patients without difference between AF recurrence and sinus rhythm groups in all follow-up period. The AF recurrence was associated with BNP levels, body mass index (BMI) and left atrial diameter (LAD) in 4-week, and BNP levels and BMI in 3-month, However, there were no factors associated with recurrence in 12-month. By multivariate regression analysis, 12-month maintenance of sinus rhythm was associated only with maintenance of sinus rhythm for the first 3 months (beta 0.664, p<0.001), but not with BNP levels or LAD. Conclusion: Plasma BNP may help to predict the recurrence of atrial fibrillation after successful electrical cardioversion in AF patients in short term period. However, the long term (12 months) maintenance is associated whether sinus rhythm is maintained for the first 3 months.