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Notes: Summary Experimental and clinical mapping studies have indicated that the initiation of atrial fibrillation has to be differentiated from the perpetuation. Curative treatment of atrial fibrillation is one of the main challenges of today's electrophysiology, and the trigger as well as the substrate have recently been targeted. The arrhythmogenic foci which have been identified as being critical for the initiation of paroxysmal atrial fibrillation have been found in the vast majority of patients in the area of the proximal pulmonary veins. In a subset of patients with paroxysmal atrial fibrillation, these firing foci may be the only electrophysiologic abnormality. In other patients, different atrial arrhythmia types may be driven by pulmonary vein foci. Haissaguerre et al. have introduced mapping strategies to identify active foci within the pulmonary veins. The success rate of percutaneous pulmonary vein focus ablation strongly depends on the number of active foci. In contrast to elimination of the initiating triggers in patients with paroxysmal atrial fibrillation, modification of the maintaining substrate of atrial fibrillation is the alternative target for ablation in patients with chronic atrial fibrillation or in patients with prolonged episodes of paroxysmal atrial fibrillation. Different linear lesion line concepts within the right and/or left atrium have been followed within the last few years with moderate success rates. The lesion geometries that have been applied percutaneously so far seem to be empirical, and no successful lesion geometry concept for percutaneous application has been validated. A surgical curative treatment concept for patients with chronic atrial fibrillation is the maze procedure introduced by Cox et.al. which, however, is an extensive and time consuming surgical technique. Within the last few years, several attempts have been made to develop alternative surgical treatment strategies that should be safe, effective, and easy to apply. One of the promising new concepts is the intraoperative radiofrequency ablation of atrial fibrillation by elemination of anatomically determined so-called anchor reentrant circuits involving the pulmonary vein orifices and the mitral annulus. In this review, data on percutaneous ablation of pulmonary vein foci, percutaneous placement of linear right and/or left atrial lesion lines and, finally, intraoperative radiofrequency (RF) ablation using minimally invasive techniques are summarized.