Introduction : Right bundle branch block(RBBB) was one of the important ECG finding in patient with acute coronary syndrome but it���s clinical implication and predictive value on cardiovascular outcomes according to various parameters is not well clarified. We aimed to clarify determine the predictive value of RBBB on clinical outcomes in patient with acute myocardial infarction from large volume nationwide registry data.Methods : We analyzed 8908 patients (male 70.4%, Age 62.4짹12.7 yr) who were presented with acute myocardial infarction and sinus rhythm at initial ECG from KAMIR(Korea Acute Myocardial Infarction Registry). We checked baseline characteristics, laboratory, echocardiographic and angiographic findings. We divided the patients into two groups according to the presence of RBBB. Various parameters and clinical outcomes were assessed during 1 year of follow up. Results : Among 8908 patients, 215 patients (2.45%) had complete RBBB in the initial ECG. In baseline clinical characteristics, patients with RBBB had higher incidence of advanced Killip class(25.6% in RBBB group vs 11.9% in non-RBBB, p=0.02). However, there was no statistically significant difference in laboratory, echocardiographic and angiographic findings between two groups except NT-proBNP(4385.3짹8896.0 in RBBB group vs 2656.8짹6363.4 in non-RBBB group, p=0.005). In survival analysis adjusted by multivariate cox regression, the presence of RBBB was independent predictor of inhospital death(p<0.001,HR=0.374) and death/myocardial infarction(p<0.001, HR=0.430) during 1 year follow up. These results were consistent in both STEMI and NSTEMI subgroup.Conclusions : The presence of RBBB in acute myocardial infarction was associated with advance Killip class higher and NT-proBNP level and was independent predictor of adverse clinical outcome. Keywords: Right bundle branch block, acute myocardial infarction, NT-proBNP