The long-term success rate of the Cox maze III procedure is excellent, although it has not been widely adopted because of the need for extensive incisions of the atria. In this study, we report our experience with a closed biatrial procedure using bipolar radiofrequency (RF) ablation for treating atrial fibrillation (AF) during non-mitral cardiac operations. Beginning in December 2004, a total of 19 patients underwent a closed biatrial procedure with bipolar RF energy. All the patients had a maze procedure plus a concomitant non-mitral operation. Except for several stabs to introduce the bipolar device, no incisions were made in either atrium. The first six patients were investigated with 64-slice multidetector computed tomography (MDCT), six months after the operation. Patients were followed-up monthly with a clinical examination and electrocardiography. There were no operative deaths. MDCT showed no evidence of coronary sinus stenosis. At one year of follow-up, 93% of the patients (14/15) were in sinus rhythm. The closed biatrial procedure using bipolar RF ablation is safe and effective in treating AF during open-heart surgery. This could be particularly beneficial for patients with AF who are undergoing a cardiac surgical procedure without opening the left atrium.