Recent studies in the clinical electrophysiology laboratory have advanced our understanding of the physiologic anatomy of the atrioventricular (AV) junction and have helped direct new curative techniques for the treatment of AV nodal (junctional) reentry. In most patients, it appears that the AV node or the inputs to the AV node that constitute the "slow" pathway are located caudal to the compact AV node and His bundle region near the os of the coronary sinus. In contrast, conduction over the "fast" pathway appears to be located along the anterior tricuspid annulus proximal to the traditional His bundle recording position. This physiologic heterogeneity has allowed the development of curative techniques for AV nodal reentry. The current preferred technique involves ablation of the slow pathway by delivering radiofrequency lesions in the region of the coronary sinus ostium. Although several different localization techniques have been developed, the overall success rate for the procedure developed, the overall success rate for the procedure includes a primary success rate that should be over 95%, a 5% to 10% late recurrence rate, and a complication rate of under 2%. Complete heart block as a complication of slow AV nodal pathway ablation is rate but can occur. The improvements in the results of radiofrequency ablation for the treatment of AV nodal reentry have resulted in the increased use of this procedure clinically. It is now reasonable to offer young patients AV nodal modification as primary therapy for AV nodal reentry and to apply the technique in all age groups to drug-resistant patients.