This study evaluates the relationship between clopidogrel related various genotyping, epidemiology and clinical outcome of patient who had undergone percutaneous coronary intervention. Clopidogrel resistance was measured with VerifyNow, which is a device that can monitor platelet inhibition of clopidogrel. Genes which are known to be related with clopidogrel resistance were evaluated; (1-3) CYP 2C19 *2, *3, *17, (4) PON1 Q192R, (5) ABCB1 3435C->T, (6) P2Y12, (7) CYP 2C9 *3.