Focal atrial and ventricular tachycardias are common diagnoses encountered in the electrophysiology laboratory. Arrhythmia burden varies from rare or paroxysmal premature beats to sustained or incessant monomorphic tachycardia. Location of the arrhythmia foci can vary, and careful contact mapping is often required to precisely locate the focus. Unfortunately, catheter ablation may fail, even when the focus is endocardial. The spatial resolution of activation mapping or pace mapping may be compromised by limitations in the steerability or reach of conventional unidirectional or bidirectional ablation catheters. The tip of a conventional steerable ablation catheter held by the operator may swing or move away from the desired ablation point with respiration and normal cardiac motion. The pressure that can be applied to ablation catheters in order to improve contact is often limited by the risk of cardiac perforation. Larger tip ablation catheters (8 mm) may be used to compensate for some of these limitations, but the accuracy of contact activation mapping and pace mapping is compromised. Magnetic robotic catheter navigation may help overcome many of the limitations of conventional catheter ablation. The Niobe ® system (Stereotaxis, Inc., St. Louis, Missouri) uses an externally applied magnetic field to direct the orientation of a catheter. The magnet system consists of two contralateral focused-field permanent neodynium-iron-boron magnets in a permanent housing that are rotated into the active position on the left and right of the patient's torso.1 In this navigational position, the magnets create a small but uniform magnetic field of 15 cm overlying the patient's heart. The field strength is 0.08 Tesla, which is several orders of magnitude less powerful than cardiac MRI magnets (typically 1.0-2.0 Tesla). In our laboratory (Figure 1), the Niobe navigation system is integrated with a monoplane flat panel system (Philips Corporation). The mapping and ablation catheter is equipped with a series of small permanent magnets that allow it to be controlled in the magnetic field.2 The catheter tip can be deflected by changing the orientation of the external magnetic field. Preset magnetic vectors based on standard cardiac anatomy can be used to direct the catheter to the desired location. In addition, custom vectors can be stored and reapplied for automatic navigation. A computer-controlled motor drive unit (Cardiodrive) is used to remotely advance and retract the catheter. The system allows precise navigation with a spatial resolution of 1 ° of omni-directional deflection and 1 mm for catheter advancement and retraction. The Navigant computer control system, located in the shielded control room, allows operators to control all aspects of catheter navigation, mapping, pacing, and ablation. The operator may control the catheter using any desired combination of the joystick control, keyboard, or mouse. The Stereotaxis system is integrated with the Carto mapping system (Biosense Webster, Inc., a Johnson & Johnson company, Diamond Bar, California), and navigation can be performed directly from the electroanatomic map or pre-procedure cardiac CT or MRI. We have found that use of the Stereotaxis Niobe system in combination with three-dimensional electroanatomic mapping is an efficient and effective approach for mapping and ablation of focal arrhythmias.