Catheter ablation has become a primary therapeutic approachfor atrial fibrillation and is more effective than purely antiarrhythmic drug treatment. Consequently, catheter ablation is increasingly becoming part of the clinical routine in many hospitals. The electrical isolation of the pulmonary veins (pulmonary vein isolation = PVI) represents the cornerstone of ablation therapy for both paroxysmal and persistent atrial fibrillation. In this context, radiofrequency ablation using the point-by-point technique is one of the most well-established methods and is accordingly widely used. This chapter focuses on pulmonary vein isolation, and detailed explanations of further ablations, such as the creation of linear lesions or other forms of substrate modification, are deliberately omitted.