Methods: Between Nov 2005 and Jan 2008 1,343 myocardial infarction patients without chest pain (66.5짹12.3 years, 63.4% men) were enrolled in a nationwide prospective Korea Acute Myocardial Infarction Registry. They were divided into two groups according to door-to-balloon time (Group I: door-to-balloon time ��� 90 min, Group II: door-to-balloon time > 90 min). Primary end points were inhospital death and 1-year major adverse cardiac events (MACE), a composite of all cause death, myocardial infarction, target lesion revascularization during 12-month clinical follow-up. Results: Patients in Group I were older (66.4짹12.1 vs 64.7짹12.2 years, p=0.040), less likely to have hypertension (44.8 vs 53.3%, p<0.001), more likely to be given primary PCI (97.7 vs 58.8%, p<0.001) and had more pre-Thrombolysis In Myocardial Infarction 0 flow (61.3 vs 30.7%, p<0.001). Other baseline characteristics have no significant differences. In multivariated logistic regression analysis, door-to-balloon time > 90 min was not one of indedpendent predictors for inhospital mortality (OR 1.01, 95% CI 0.24-4.17, p=0.993). In Cox proportional hazards analysis, door-to-balloon time >90 min reduced MACE in significant degree (HR 0.61, 95% CI 0.38-0.99, p=0.044). But after adjustment of confounding variables using propensity score analysis, we found out that door-to-balloon time was not related with clinical outcomes in painless MI patients (HR 0.63, 95% CI 0.39-1.02, p=0.059). Conclusion: Early PCI after admission had no beneficial effect on the short- and long-term clinical outcomes in patients with painless MI. Early detection of ischemic onset before hospital presentation could be more important. Effective methods to detect painless MI should be developed so that we can reduce the ischemic duration.