The paracardioscopic ex-maze (PEX) procedure is a totally endoscopic, minimally invasive surgical procedure for the correction of all types of atrial fibrillation. The PEX is performed on the epicardial surface of the beating heart without the use of cardiopulmonary bypass. Access to the pericardium is via a novel transdiaphragmatic approach using a cannula to access the posterior heart. Additionally, right chest thoracoscopy provides access to the right epicardium to complete a bi-atrial ablation pattern. A unipolar, irrigated radiofrequency device is used to create the epicardial lesions. Because the lesions are created on the epicardium, lesion contiguity can be verified by visual observation. Also, as the heart is beating, conversion to sinus rhythm can be directly observed during the procedure and pulmonary vein isolation/exit block can be verified after lesion creation.