Since Haïssagere and colleagues reported that a rapid firing focus in or close to the pulmonary veins could be the cause of atrial fibrillation, a transcutaneous catheter technique directed at isolating these foci has been developed. How should patients with nonvalvular atrial fibrillation who require cardiac operation be managed? We developed an epicardial technique that uses cryoablation to isolate the left atrial posterior wall and pulmonary veins and used it to treat a patient. Because cryoablation is achieved epicardially, the technique does not require atriotomy and does not prolong aortic cross-clamp time. Isolation of the left atrium was confirmed by electrophyscologic studies, and the patient remains in sinus rhythm 16 months after operation. This concomitant procedure allows treatment of patients with nonvalvular atrial fibrillation.