Trial to Assess the Efficacy of Combination Formula of Aspirin Plus Clopidogrel in Patients With Coronary Stent

Inclusion Criteria: * Over 3 months, the patient who were the administration of aspirin or the co-administration of clopidogrel-aspirin coronary artery patients after treated with Percutaneous Coronary Intervention(PCI) that have safety progress. * Korean men and women between the age of 20 and 85 * Patients who understand the study requirements, are willing to comply with all study procedures and have provided written informed consent. Exclusion Criteria: * Patients who were not treated with PCI or intended to treat with PCI but failed. * Patients who were taking or had taken other antiplatelet or anticoagulant for more than 2 weeks within the prior 30 days. * Patients who had a history of alcohol abuse or intoxication. * Patients who had hypersensitivity to clopidogrel or aspirin. * Patients who had severe hepatic dysfunction aspartate aminotransferase(AST) or alanine aminotransferase(ALT) \> 3 times upper normal reference values. * Patients who had blood coagulation disorders, uncontrolled severe hypertension, active bleeding, or history of severe bleeding, such as intracranial hemorrhage or ulcer bleeding - surgery within 48hr, platelet counts below 50,000/mm3 in laboratory tests. * Patients who were pregnant, breastfeeding. * Patients who were not using effective methods of contraception. (proper contraception : hormonal contraception, condom, intrauterine device, spermicide) * Patients who medically, psychologically had investigational product administration's prohibition. * Patients who were not participated in this clinical trial decided by other investigators.