Background We explored the efficacy and the electrophysiologic characteristics of antral ablation (AA) of the left atrium (LA) in conjunction with electrical isolation of pulmonary veins (PV), and compared it with circumferential ostial ablation of PV (OA) in patients with atrial fibrillation (AF). Methods and Results We compared AA and OA in 32 patients (Male 27, mean age 51짹14 years) with AF (23 paroxysmal AF (PAF), 9 persistent AF) who underwent radiofrequency catheter ablation (RFCA). For AA (n=17, 14 PAF), the LA antrum was ablated circumferentially guided by 3D mapping system and then PV potentials (PVPs) were eliminated by additional ablation with Lasso catheter guidance. For OA (n=15, 9 PAF), we eliminated PVPs by Lasso guided RFCA encircling PV ostia. Results. 1. The procedure time for electrical isolation of all PVs was significantly shorter in AA (94짹35 min) than in OA (149짹58 min, p<0.001), but there was no significant difference in the number of RF lesions (78.5짹22.3 in AA vs. 96.4짹39.4 in OA, p=NS). 2. Immediately after circumferential RFCA at both antra in AA, all PVPs disappeared or dissociated in only 19.3% of PVs (3.4% of upper PVs vs 35.7% of lower PVs, p<0.01). The maximal interval between LA potentials and remaining PVPs measured by Lasso electrogram was markedly delayed (61.9짹23.5 ms), and the number of polarity reversals was 2.0짹1.2 during sinus rhythm (SR). Required number of RF delivery for PVPs elimination was smaller in AA (7.4짹9.4 per PV) than in OA (30.7짹24.7 per PV, p<0.001). 3. Post-RFCA inducibility of atrial arrhythmia by rapid atrial pacing was not different between two groups (35.3% vs 35.3%), whereas the induced atrial tachycardia (AT) was more common in AA than in OA (83.3% vs 0%, p<0.001). 4. During 5.8짹1.7 month of follow-up, 88.2% (15/17) of AA and 86.7% (13/15) of OA remained in SR (76.5% antiarrhythmic drug-off in both groups, p=NS), respectively. A case of clinically significant PV stenosis was documented only after OA. Conclusion Circumferential antral ablation in conjunction with electrical isolation of PV (AA) is faster and highly effective as electrically guided OA without risk of PV stenosis during short-term follow up.