Background The clinical outcomes of patients with acute myocardial infarction (AMI) involving left main coronary artery (LMCA) as culprit vessel are disastrous. The aim of this study is to evaluate the one year clinical outcomes and its predictors of LMCA related AMI. Materials and Methods A total of 255 patients diagnosed as AMI involving LMCA as a culprit vessel and registered to Korean Acute Myocardial Infarction Registry were enrolled in this study. The patients were divided according to presence of cardiogenic shock at their initial presentation (Group 1, n=211) and with it (Group 2, n=44). One year clinical outcomes of major adverse cardiac events (MACE) such as cardiac death, myocardial infarction, target lesion revascularization (TLR), target vessel revascularization (TVR) and stent thrombosis (ST) were evaluated between two groups. Independent risk factors of in-hospital cardiac death associated with LMCA related AMI were elucidated by multivariate regression analysis Results Baseline characteristics were not different. Initial in-hospital mortality rates were 8.5% in Group 1 and 45.5% in Group 2 (p=0.001). On multivariate analysis, initial shock presentation (p=0.004, Odds ratio 8.9, C.I. 4.1~19.2) and left ventricular ejection fraction less than 30% (p=0.001, Odds ratio 7.6, C.I. 2.7~21.1) were independent risk factors of in-hospital cardiac death associated with LMCA related AMI. MACE was developed 16.3% in Group 1 and 18.2% in Group 2 (p=0.828). Cardiac death, non-fatal myocardial infarction, TVR or TLR were similar between two groups. ST was developed in 2% in Group 1 and 4.5% in Group 2 (p=0.448). Conclusions The clinical outcomes of patients with AMI related with LMCA were fatal. Although cardiogenic shock contribute to the higher in-hospital mortality, the clinical outcomes after survival were not different. Key Words: Acute Myocardial Infarction, Left main, Outcomes