A novel approach to localize the origin of a right ventricular outflow tract tachycardia using an ablation catheter having an orthogonally oriented electrode array is described. Bipolar electrogram polarity reversal using minimally filtered (1-500 Hz) electrograms simultaneously acquired in two axes from the ablation catheter permitted accurate localization of the tachycardia focus. A single radiofrequency energy application at the site identified by this technique resulted in successful tachycardia ablation. This technique may facilitate mapping of any arrhythmia which can be modeled as arising from a point source.