Background: In patients with non-ST-elevation myocardial infarction (NSTEMI), current guidelines did not recommend optimal revascularization management in multivessel coronary artery disease. We compared clinical outcomes between multivessel revascularization and culprit-only revascularization in this setting. Methods: A total of 1,919 patients with multivessel disease (1,011 patients; multivessel revascularization group, 908 patients; culprit-only revascularization group) diagnosed as NSTEMI was enrolled in a nationwide prospective Korea Acute Myocardial Infarction Registry (KAMIR) from November 2005 to January 2008. The primary end points were major adverse cardiac events (MACE), all-causes of deaths, myocardial infarction (MI), and repeated percutaneous coronary intervention (PCI) during 1-year clinical follow-up. Also, subgroup analysis was performed in patients with high TIMI (Thrombolysis In Myocardial Infarction) risk score (���4) to find efficacy of multivessel PCI in high risk patients. Results: Baseline clinical characteristics and the risk factors of coronary artery disease were similar between both groups. In angiography, three vessel lesion was more presented in multivessel group (46.1% vs. 40.9%, p=0.024) and rates of left anterior descending and left main stem coronary artery as culprit vessel were higher in multivessel group (p=0.003 and p=0.001 respetively). In-hospital mortality was higher in culprit-only group (1.4% vs. 2.9%, p=0.025). Primary end-points occurred in 241 patients (15.5%) during 1-year follow-up. Multivessel revascularization reduced MACEs [hazard ratio (HR) 0.658, 95% confidence interval (CI) 0.45 to 0.96, p=0.031], death or myocardial infarction (HR 0.58, 95% CI 0.35 to 0.97, p=0.037) and non-target vessel revascularization (HR 0.44, 95% CI 0.24 to 0.81, p=0.008). There were no significant differences in target lesion revascularization (TLR; HR 1.38, 95% CI 0.51 to 3.71, p=0.529) and target vessel revascularization (TVR; HR 0.28, 95% CI 0.05 to 1.47, p=0.131). In subgroup analysis in patients with higher TIMI risk score, similar results were presented. Conclusion: Multivessel revascularization in multivessel coronary artery disease presenting with NSTEMI showed better clinical outcomes without significant in-stent restenosis and progression of diseased-vessel compared to culprit-only revascularization. KEYWORDS: Myocardial infarction; Coronary artery disease; Angioplasty, Percutaneous coronary intervention