Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice and is estimated to affect 2.2 million people in the United States. AF is a major cause of stroke, adversely affects quality of life, and is associated with increased mortality. Despite advances in antiarrhythmic drug therapy, AF continues to be associated with significant morbidity. Although antiarrhythmic drug therapy is currently considered a first-line option, recent data indicate that more than 35% of Patients will have recurrence of AF despite best antiarrhythmic drug (AAD) therapy, and more than 30% of Patients will discontinue the drugs because of adverse reactions. Furthermore, although recent trials have indicated equivalence of rhythm and rate control strategies in some patient populations, 25-35% of Patients with AF who are rate controlled will continue to have activity limiting symptoms. Newer measures to prevent, treat and potentially cure AF are needed. Seminal work by Haissaguerre and replicated by Chen showed that the majority of AF is initiated by ectopic foci found primarily in the pulmonary veins (PV). Experience with the catheter-based Maze technique led to observations that opened the door to effective and practical catheter-based cures for AF. In response to the difficulties of focal ablation, an alternate strategy has been developed that seeks to electrically isolate the Pulmonary Veins from the atrial tissue. Empirical PV isolation targets all of the PV's without regard to the initiation of ectopic beats. The goal is to create entrance block in the PV. Multipolar circular catheters and basket catheters have been developed that facilitate identification of the electrical connections that are present at the junction of the atrium and the PV, and radiofrequency energy is applied in a circumferential fashion until entrance block is achieved. Relative to focal ablation, circumferential PV isolation is simpler to perform, can be completed without inducing AF, has a shorter procedure time, and has a lower incidence of PV stenosis.