Objectives: We compared early and late clinical outcomes of simultaneous complete revascularization vs. culprit only revascularization in patients with acute ST-elevation myocardial infarction (STEMI). Background: The optimal percutaneous interventional strategy for dealing with significant non-culprit lesions in patients presented with STEMI and concomitant multivessel disease remains to be controversial. Methods: A total of 299 patients presented with acute STEMI and multivessel disease underwent percutaneous coronary intervention (PCI) between March, 1997 and March, 2006. Among the overall patients, 82 patients (27%) underwent simultaneously complete revascularization for culprit and the other significantly narrowed arteries, and 217 patients (73%) had undergone PCI for culprit lesion only and the other diseased artery were deferred during the primary PCI. Results: At 30 days after the procedure, the rates of death (2.4 versus 7.4%, adjusted hazard ratio [HR], 0.22, 95% confidence interval [CI] 0.05 to 0.99, P=0.05), MI (1.2 versus 1.9%, adjusted HR, 0.21, 95% CI 0.01 to 3.42, P=0.28), and stent thrombosis (2.4 versus 2.8% adjusted HR, 0.45, 95% CI 0.07 to 2.68, P=0.45) did not significantly differ among patients with simultaneous completer revascularization or not. During 4 years of follow-up, patients with complete revascularization during primary PCI showed lower rate of death (4.9 versus 20.9%, adjusted HR, 0.15, 95% CI 0.03 to 0.69, P=0.01) and death or MI (8.5 versus 25.1%, adjusted HR, 0.31, 95% CI 0.11 to 0.84, P=0.02) as compared with those without. Conclusion: In the setting of primary PCI for STEMI with concomitant multivessel coronary disease, simultaneous complete revascularization for culprit and non-culprit lesions showed better long-term survival rate as compared with revascularization for culprit lesion only.