Background and Objectives: Although there is an agreement that hyporesponsiveness or resistance to antiplatelet agents associates with increased risk of adverse events but the definition of hyporesponsiveness by laboratory assays may not correlate with clinical events. We evaluated the impact of laboratory measurement of platelet function on long-term cardiovascular events in patients who underwent drug-eluting stents insertion. Subjects and Methods: Total of 200 patients, who underwent percutaneous coronary intervention (PCI), were examined platelet-function tests after intake of loading dose of 300-mg aspirin and 300-mg clopidogrel. Aspirin and clopidogrel resistance were defined as aspirin reaction units (ARU) of ���550 and P2Y12 reaction units (PRU) of ���240, respectively. Then the major adverse cardiovascular events (MACE) were investigated at 30 days, 6 and 12 months after PCI, followed by administration of routine maintenance dose of aspirin and clopidogrel. Results: In comparison of baseline and procedural characteristics, the percentage of women, elder patients (age of >70) and diabetes were higher in non-responder group. Other parameters did not show any significant differences in both groups. The rate of resistance to aspirin, clopidogrel and both drugs was 6.4%, 37.2% and 3.7%, respectively, with total resistance rate of 47.3%. There was no significant difference in the comparison of rate of MACE in both responder and non-responder. However, dual low response to both drugs showed higher rate of MACE, approximately 28.6%. Conclusions: Initial laboratory assay of platelet function alone to classify patients into low or high risk group of adverse ischemic events has a low predictive power. We might need to develop a risk score system to predict a prognosis, including several parameters of women, diabetes, elder, renal function, dual low response, and CYP2C19 polymorphism. Key words: Platelet function tests, Drug-eluting stents, Coronary intervention