Background: Optimal treatment strategy of patients with acute myocardial infarction (AMI) and multivessel disease (MVD) undergoing primary angioplasty is still unclear. We compared in-hospital and long-term outcomes for patients with AMI and MVD treated by primary percutaneous coronary intervention (PCI) of non-culprit vessels simultaneously or soon after PCI for culprit artery. Methods: 270 AMI with MVD patients (mean age=63.1짹11.3 years, 197 males) treated by primary PCI divided into two groups. The group I (n=90, 61.3짹12.6 years, 66 males) was single staged PCI group (PCI of non-culprit vessels was done simultaneously with PCI of culprit vessel) and the group II (n=180, 63.9짹10.5 years, 131 males) was multi-staged PCI group (PCI of non-culprit vessels was done at some days after PCI of culprit vessel). Major adverse cardiac events (MACEs) at one-year clinical follow-up were defined as a composite of all-cause death, re-infarction, coronary artery bypass grafting, heart failure requiring rehospitalization, and target lesion revascularization. Results: Group II patients underwent staged PCI at 7.8짹6.3 days after primary PCI. 46 (51.1 %) patients had ST-segment elevation MI (STEMI) and 44 patients had non-STEMI. 19 (21.1 %) patients had two-vessel disease and 71 patients had three-vessel disease in group I. 131 (72.8 %) patients had STEMI and 49 patients had non-STEMI. 84 (46.7 %) patients had two-vessel disease and 96 patients had three-vessel disease in group II. The baseline clinical characteristics were similar between two groups. Group I had a higher rate of in-hospital death compared with the group II [5.6 % vs. 0.0 %, relative risk, 3.115; 95 % confidence interval (CI), 2.62 to 3.72; p=0.001]. And the incidence of MACE during one-year clinical follow-up period was higher in group I compared with the group II. (22.2 % vs. 11.7 %, relative risk, 2.165; 95 % CI, 1.10 to 4.24; p=0.023). The increment of ejection fraction at follow-up echocardiography was 5.1짹14.6 % in group I and 1.7짹11.1 % in group II (p=0.145). Conclusions: In management of non-culprit vessel, elective second staged intervention was more feasible and safe rather than single staged PCI.