Background: It is well established that high blood glucose level is closely correlated with major adverse cardiovascular events (MACE). The purpose of this study is to evaluate whether casual blood glucose level at admission affects the clinical outcomes in Korean patients with ST-elevation myocardial infarction (STEMI). Methods: 1735 consecutive patients with STEMI, who were recruited in KAMIR between Oct 2005 to Jun 2007 was included(61짹12 years). The patients without prior diabetes mellitus (DM) history divided into three groups according to casual blood glucose levels at admission(Group I: <140 mg/dL, Group II: 140 - 200 mg/dL, Group III: glucose ���200 mg/dL). And composite MACE as well as non-cardiac mortality was compared among these 3 groups. Results: Success rate of PCI and baseline risk factors such as hypertension, smoking, and hyperlipidemia were not significant differences among the three groups. MACEs at 1-month, 6-month, and 1 year increased in accordance with glucose level (p<0.01, p<0.01, p<0.01, respectively). Among 1 year MACE, all-cause mortality (2.8% vs 3.3% vs 5.6%, p<0.01) and cardiac death (0.5% vs 0.7% vs 1.3%, p<0.001) was significantly different with each glucose group. Target lesion revascularization (TLR) and target vessel revascularization (TVR) rate was not significantly different between the 3 groups. In Kaplan-Meyer survival analysis, there were significant differences (p<0.05, by log-rank test) and group 3 shown worser outcome. In Cox-proportional hazard model, the hazard ratios of 3 groups were 1.00, 1.26 (95% CI 0.63-2.53), 2.14 (95% CI 1.08-4.25), respectively. In logistic regression analysis, age (p<0.001, OR 1.07, 95% CI 1.03-1.10) and casual blood glucose level (p=0.001, OR 1.01, 95% CI 1.00-1.01) were independent parameters of all-cause mortality. But, by subgroup analysis according to admission HbA1c level (divided to HbA1C < or >7 %, n=200), there were no significant differences in 1-month MACE and 1 year mortality. Conclusions: Admission blood glucose, not HbA1C, could be a reliable predictor for prognostic value and associated with long-term mortality in Korean patients with STEMI.