Focal atrial tachycardia (AT) arising from non-coronary cusp (NCC) is very rare, and the experience in catheter ablation of this kind of tachycardia remains limited. This study describes the electrophysiologic characteristics and radiofrequency ablation of AT arising from NCC. The study population consisted of five consecutive patients (three females and two males; age 37-68 years) with AT arising from NCC. The morphology of P waves was described as positive, negative, isoelectric, or biphasic (positive-negative or negative-positive). The atrial mapping was performed during tachycardia to define the earliest atrial activation site. Mean tachycardia cycle length of AT in five patients was 363 +/- 44 ms. P-wave morphology was predominantly upright or biphasic in lead II, III, and aVF, inverted in aVR. Positive P-wave morphology was seen in lead aVL in all five patients. The precordial leads were negative-positive in V-1 and V-2, negative-positive or positive in lead V-3-V-5, and positive in lead V-6. All the five patients underwent successful radiofrequency ablation within NCC. During a follow up of > 3 months, no patient presented with a recurrence. This study demonstrated that mapping and ablation of focal AT arising from NCC is safe and effective. When earliest activation was recorded in the proximal electrode of the His-bundle catheter, but radiofrequency ablation in this region cannot successfully eliminated the tachycardia, the AT should be considered to arise from NCC especially when P-wave morphology was initially negative with a late positive component in right precordial leads, upright or biphasic in inferior leads.