Background: The aim of this study was to assess the relationship between glucose level at admission and prognosis in patients with acute myocardial infarction(AMI). Methods: A total of 7,209 AMI patients were enrolled between Nov. 2005 and Jan. 2008. The patients were divided into two groups according to admission serum glucose levels: group I (<200 mg/dL, n=5,502), and group II (>200mg/dL, n=1,707). Incidence of MACE (death, MI, target lesion revascularization) in in-hospital, 1 month, 6 months and 12 moths were compared between the groups. Results: There were no significant differences in clinical characteristics between the groups except the incidence of diabetes mellitus (DM). Incidence of DM was 1,056 (19.2%) in group I and 887 (52%) in group II(p<0.001). The patients who underwent PCI were 4, 674 (85%) in group I and 1,431(83.8%) in group II (p=NS). Group II showed significantly higher in-hospital mortality than group I (p<0.001) and in-hospital mortality showed progressively increased with higher tertiles of elevated serum glucose level at admission. But there were no significant differences in incidence of MACE at 1month, 6 months and 12 months follow up. After multiple regression analysis including clinical characteristics, PCI and success of PCI, etc, the acquisition of final TIMI 3 flow after PCI (p=0.001, OR 0.26, C.I. 0.13-0.49) and presence of hyperglycemia at admission (p=0.005, OR 2.25, C.I. 1.28-3.95) were the independent predictor of in hospital death. Conclusion: We found significant association between admission glucose levels and in-hospital mortality in a large cohort of patients with AMI. Our findings suggest that we should pay more attention to control the hyperglycemia at admission even in non-diabetic patient.