Background: There is limited evidence on optimal therapy for patients undergoing PCI with underlying atrial fibrillation(AF) which needs antithrombotic and post-PCI antiplatelet therapy. We evaluated the efficacy and safety of triple anticoagulation therapy (TAC) compared to dual anticoagulation therapy (DAC) or dual antiplatelet therapy (DAP) in patients undergoing PCI with AF. Method: We selected 78 patients who had taken post-PCI antiplatelet therapy and had underlying AF with CHADS2 risk score ��� 2 from 1999 to 2008. We assessed the incidence of embolic stoke, major hemorrhage and prothrombin time (PT INR) by medical record and phone contacts. Result: Of the drug prescribed around PCI, TAC (aspirin + clopidorel + warfarin) was prescribed in 27 patients (34.6%), DAC (warfarin + aspirin or warfarin + clopidogrel) was in 28 patents (35.9%), DAP (aspirin + clopidorel) was in 23 patients (29.5%). There was no defference in the incidence of major hemorrhage between treatment groups (TAC: 3.7%, DAC: 7.1%, DAP: 8.7%, p=0.785). The embolic stoke was less frequently developed in TAT group (3.7% vs. 7.1% vs. 30.4%, p<0.01). PT INR of patients with major hemorrhage was 2.094 짹 0.61 and that of without was 2.027 짹 0.62. No difference was found between two groups(p=0.813). Conclusion: Triple anticoagulation therapy for the patients undergoing PCI with underlying atrial fibrillation may be more beneficial than other combinations by reducing the incidence of embolic stroke.