Background: Statins has been suggested to protect against atrial fibrillation (AF) in some clinical observational and experimental studies, but has remained inadequately explored. This analysis from the Korean Acute Myocardial Registry (KAMIR) assessed the beneficial effects of statin therapy for reduction of MACE in AMI patients with presenting AF. Methods: 559 AMI patients (mean age = 69.1 짹 11.6 years, 370 males) who were presented with AF on EKG at arrival in the emergency room were divided into two groups; statin treatment group (n = 364, 68.9 짹 11.4 years, 247 males) or control group (n = 195, 69.3 짹 12.1 years, 123 males). We retrospectively evaluated the effects of statin therapy on MACE including all-cause death, re-infarction, coronary artery bypass grafting, heart failure requiring re-hospitalization, and target lesion revascularization during in-hospital period and one-year clinical follow-up. Results: The statin treatment group was 187 (51.4 %) of ST segment elevation MI (STEMI) and 177 of non-STEMI (NSTEMI) and control group was 109 (55.9 %) of STEMI and 86 of NSTEMI. The baseline clinical characteristics were similar between the two groups including hemodynamic parameters, killip class, risk factor of atherosclerosis, EKG and echocardiographic, and coronary angiographic findings. The baseline level of LDL cholesterol was higher in statin treatment group than control group (107.9 mg/dl vs. 96.8 mg/dl, p=0.003). The baseline levels of high-sensitivity C-reactive protein and N-terminal pro brain type natriuretic peptide were not significantly different between the groups. The rate of in-hospital death was significantly lower in statin treatment group (5.5 % vs. 23.8%, p<0.001). The incidence rate of MACE during one-year clinical follow-up was significantly lower in statin treatment group (11.8 % vs. 27.7 %, p<0.001). Multivariate Cox regression analysis revealed that statin therapy (P=0.015, hazard ratio: 0.51; 95% confidence interval: 0.31-0.85) was a significant predictor of favorable prognosis. Conclusion: Statin therapy was beneficial for long-term outcome of AMI patients with AF.