Several studies have shown the role of focal trigers in the pulmonary veins initiating episodes of atrial fibrillation. Radiofrequency catheter ablation of this foci is a curative therapy for paroxysmal atrial fibrillation. We report a case of idiopathic paroxysmal atrial fibrillation triggered by abnormal electrical activity in a single pulmonary vein. Mapping was performed during sinus rhythm with a 4F decapolar catheter (Spiral Supreme, Daig, St. Jude Medical) positioned near the ostium by a transseptal approach. Pulmonary vein potentials were only identified in the left superior pulmonary vein. Segmental ostial ablation (30 W) performed during left atrial pacing resulted in complete cesation of conduction in the pulmonary vein. There were no complications. The clinical response (suppression of the paroxysms of atrial fibrillation in a 9-month follow-up) observed in this patient imply that atrial fibrillation was triggered by this pulmonary vein. This case report illustrates several aspects of catheter-based ablation of pulmonary vein foci for the treatment of paroxysmal atrial fibrillation and demonstrates its efficacy.