Background: The optimal timing of coronary artery bypass graft surgery (CABG) after acute myocardial infarction (AMI) remains controversial, although it has been common practice to wait for days to weeks in non-urgent cases to allow for myocardial recovery. Objective: We assessed the effect of CABG timing on short-term clinical outcomes in AMI patients. Subjects and Methods: A total of 387 patients, enrolled in the nationwide prospective Korea Acute Myocardial Infarction Registry between November 2005 and January 2008, were grouped into early and late groups based on the median time from admission to CABG. The primary endpoint was in-hospital mortality. Regression adjustment with propensity scores were applied to control for factors associated with clinical urgency before CABG, including ventricular tachycardia/fibrillation (VT/VF) on admission, mechanical complications of AMI, intra-aortic balloon counterpulsation (IABP), mechanical ventilation, left ventricular ejection fraction (LVEF), location of culprit lesions, and failed percutaneous coronary intervention (PCI). Results: The median time of CABG was 3 and 6 days in ST-elevation MI (STEMI) and non-ST-elevation MI (NSTEMI), respectively. In STEMI, early CABG group (<3 days, N=80) had significantly higher rates of in-hospital death (17.5% vs. 6.0%, p=0.021), failed PCI (19.6 vs. 6.6%, p=0.023), cardiogenic shock (11.3% vs. 1.2%, p=0.007), and IABP (26.3% vs. 8.3%, p=0.002). Late group (���3 days, N=84) had higher rates of thrombolysis (16.7% vs. 3.8%, p= 0.007) and multi-vessel disease (96.1% vs. 73.2%, p <0.0005). After adjustment, however, in-hospital mortality was similar between early and late groups (p=0.457). Predictors of mortality were age, Killip class IV, and VT/VF on admission. In NSTEMI, early group (< 6 days, N=113) had higher rates of IABP (15.0% vs. 6.4%, p=0.037) and mechanical ventilation (13.3% vs. 4.5%, p=0.023), compared to late group (���6 days, N=110). After adjustment, in-hospital mortality was not different between the two groups (11.5% vs. 7.5%, p=0.450). Mechanical ventilation before CABG was a predictor of mortality in NSTEMI. Conclusion: In patients with AMI undergoing non-urgent surgical intervention, early CABG within two to five days may be considered without increased mortality risk, compared to CABG performed later.