This report describes a patient who underwent RF catheter ablation of atrial tachycardia. Two applications of RF energy near the His-bundle region transiently terminated the tachycardia. With detailed mapping at the aortic sinus of Valsalva using a retrograde transaortic approach, the earliest atrial activation was found in the noncoronary sinus of Valsalva. Complete elimination of the tachycardia was achieved with RF energy application from this site.