Objective: Chronic atrial fibrillation (AF) is a frequent arrhythmia in patients undergoing open-heart surgery. In this study, we compared the results of irrigated monopolar and bipolar radiofrequency (RF) ablation in the surgical treatment of AF. Methods: Sixty-three patients with chronic AF, who underwent open cardiac surgery and concomitant irrigated RF ablation between October 2004 and January 2006, were retrospectively studied in two groups. Group 1 included 31 patients (22 female, 9 male), who underwent monopolar RF ablation, and Group 2 included 32 patients (18 female, 14 male), who underwent bipolar RF ablation. All patients received amiodarone during the first 6 months after surgery. Rhythm status of patients after RF ablation was followed-up postoperatively in the intensive care unit, on the day of discharge, and at their follow-ups with electrocardiography. In patients with a documented sinus rhythm (SR) at follow-up, the presence of atrial transport function was assessed with transthoracic echocardiography. Statistical analyses were performed by using t-test for independent samples, Chi-square test and McNemar's test. Complication-free survival during follow-up was evaluated using Kaplan-Meier analysis. Results: There was no hospital mortality in both groups. One patient from Group 1 had non-cardiac mortality (colon carcinoma). While in monopolar ablation group SR was documented in 83.3% of patients at a mean follow-up period of 11.5±4.0 months (between 4-18 months), 68.8% of patients from bipolar ablation group was in SR at a mean follow-up period of 9.3±3.0 months (between 4-15 months). In patients with documented SR during follow-up visits, atrial transport function was 76.6% in cases undergoing monopolar ablation, whereas it was 72.7% in cases undergoing bipolar ablation (p=0.797). Pacemaker implantation was performed in one (3.4%) patient from Group 1 after hospital discharge and in one (3.1%) patient from Group 2 during hospital stay. Conclusion: Irrigated monopolar and bipolar RF ablation are both safe and effective in terms of restoring SR and atrial transport function in patients with chronic AF, who underwent open cardiac surgery.