The Optimal Duration of Dual Antiplatelet Therapy After Implantation of Endeavor Stent

Inclusion Criteria: * Patients with clinically significant de novo coronary artery disease * Stenting only with Endeavor® stents * The sum of stent length is less than 60 mm for one lesion. The sum of stent length in multiple lesions does not matter. Exclusion Criteria: * Cardiogenic shock * ST-elevation myocardial infarction within 48 hours of symptom onset * Prior implantation of drug-eluting stents * Left ventricular dysfunction (echocardiographic left ventricular ejection fraction \< 25%) * Stenting both branch of bifurcation lesion * Left main trunk lesion * Graft vessels * Patients who have to receive clopidogrel due to other conditions * Patients who have to receive warfarin, cilostazol or other antiplatelet therapy * Patient with chronic renal failure (S-Cr \> 2.0 mg/dl) * Hypersensitivity to clopidogrel or aspirin * Expectant survival less than 1 year * Women who plan to become pregnant * Patients with bleeding diathesis (coagulopathy, thrombocytopenia or platelet dysfunction, Gastrointestinal or genitourinary bleeding within the prior 3 months) * Patients who are actively participating in another drug or device investigational study, which have not completed the primary endpoint follow-up period.