The radiofrequency Maze procedure can effectively restore sinus rhythm in most patients with atrial fibrillation (AF) and mitral valve disease. AF after cardiac surgery is associated with increased morbidity and mortality. However, clinical determinants of long-term postoperative AF after the radiofrequency Maze procedure and concomitant mitral valve surgery are poorly defined. This study comprised 99 consecutive patients with persistent AF and mitral valve disease who underwent radiofrequency Maze procedures and concomitant mitral valvular operations. The predictive values of clinical variables for postoperative AF were examined. After a mean follow-up period of 46.1+/-24.6 months, 83 patients (83.8%) had sinus conversion after the Maze procedure, and 16 patients remained in persistent or paroxysmal AF. Multiple logistic regression analysis determined that predictors of sinus conversion were preoperative left atrial diameter (odds ratio [OR] 1.127 per 1-mm increment in left atrial diameter, 95% confidence interval [CI] 1.045 to 1.215, p<0.002) and the duration of AF (OR 1.022 per 1-month increment in duration of AF, 95% CI 1.009 to 1.035, p<0.001). Discriminant analysis showed that the sinus conversion rate was significantly lower in patients with preoperative left atrial diameters>56.8 mm (p<0.001) or AF duration>66 months (p<0.001) than in patients with preoperative left atrial diameters<56.8 mm or AF duration<66 months. In conclusion, the preoperative left atrial size and duration of AF are primary predictors of sinus conversion by the radiofrequency Maze procedure for patients with persistent AF and mitral valve disease.