The advent of catheter ablation stimulated extensive research into anatomical localization of the pathways involved in atrioventricular nodal reentrant tachycardia (AVNRT). Conventional electrophysiological methods that attempt to correlate intracardiac electrograms with two-dimensional fluoroscopic anatomy are limited by the relative inaccuracy and poor reproducibility of this technique, and the requirement for high levels of radiation exposure. A new method of nonfluoroscopic electroanatomical mapping utilizes magnetic field sensing with a specialized catheter to construct three-dimensional electroanatomical endocardial maps of selected heart chambers with spatial resolution of < 1 mm. This system can be used in patients undergoing catheter ablation for AVNRT to create accurate maps of Koch's triangle and to guide application of radiofrequency energy. Initial experience in 14 patients suggests efficacy and safety comparable to conventional mapping and ablation techniques. Further evaluation may confirm the potential benefits of this system with respect to success rates, complications, procedure time, and radiation exposure.