Background: Circulating lipids appear to have prothrombotic and endothelium-altering properties. Atrial fibrillation is associated with thromboembolism, endothelial dysfunction and abnormalities in coagulation system. However, it is not certain whether statin may reverse prothombotic condition in atrial fibrillation. Methods: Consecutive 306 atrial fibrillation patients were enrolled. Patients of group I had dyslipidemia and received statin for more than 6 months (n=122, 59짹11 years) and group II had not dyslipidemia and did not receive statin (n=184, 56짹17 years). Markers for endothelial function (von-Willebrand factor, vWF; factor 8 related antigen and ristocetin cofactor), inflammation [WBCs, ESR, quantitative and high sensitivity C-reactive protein] and coagulation system (fibrinogen, fibrinogen degradation product, fibrin d-dimer) and platelet activity (p-selectin) were measured. Results: There were no significant differences in levels of markers for endothelial dysfunction or inflammation between 2 groups. Total and LDL-cholesterol levels were significantly higher in group I than in group II (185짹44 mg/dL vs 169짹35 mg/dL, p=0.001 124짹45mg/dL vs 102짹29mg/dL, p=0.001). Even though fibrinogen level was not different between 2 groups (group I; 303짹88 mg/dL, group II; 287짹84 mg/dL, p=0.107), fibrinogen degradation product level was significantly lower in group I (1.1짹1.7 ug/mL vs 2.2짹4.6 ug/mL, p=0.024). D-dimer level also was significantly lower in group I than group II (0.19짹0.19 mg/L vs 0.27짹0.29 mg/L, p= 0.013). Conclusion: Statin showed beneficial effect on coagulation system in patients with atrial fibrillationregardless of their cholesterol level and statin may reduce thromboembolism in patients with atrial fibrillation and dyslipidemia.