Assessment of the timing of electrical activation recorded by multiple electrodes positioned in various locations within the heart has been the conventional method for mapping cardiac arrhythmias. This technique requires fluoroscopy for catheter manipulation, which in addition to being harmful (ionizing radiation), is inadequate for visualizing the complex three-dimensional cardiac anatomy and lacks reproducibility regarding localization of sites of interest. Because of these limitations, several new mapping systems that can function in a complimentary role to the conventional mapping technique, or can be used independently, have been developed. These new mapping strategies have unique advantages. They overcome the limitations of fluoroscopy by creating accurate three-dimensional intracardiac maps. The ability to localize and accurately display intracardiac catheter positioning and ablation lesion sites facilitate increasingly complex catheter ablation procedures.