Background: Although some serum markers have been reported to be correlated with thromboembolic risks of atrial fibrillation (AF) along with some clinical and echocardiographic parameters, it is not certain what kind of mechanism plays the most powerful role in developing thromboembolism (TE). Subjects and Methods: The enrolled patients were persistent and permanent AF (M:F=39:35, 53짹18 years). Risk factors for TE were defined as old age (��� 65 years), diabetes mellitus, hypertension, heart failure, valvular heart disease, left ventricular dysfunction, history of TE. Markers for endothelial function [von-Willebrand factor, vWF (factor 8 related antigen, ristocetin cofactor), thrombomodulin], inflammation (white blood cell counts, erythrocyte sedimentation rate, quantitative and high sensitivity (hs) C-reactive protein, interleukin-6), coagulation (fibrinogen, fibrinogen degradation product, fibrin d-dimer) and platelet activation (p-selelctin) were measured. Results: vWF-factor 8 related antigen was increased as increasing age (r=0.529, p=0.000), NYHA class (r=0.394, p=0.007), left atrial size (r=0.482, p=0.006) and more increased with presence of hypertension (171짹48% vs. 128짹59%, p=0.019), congestive heart failure (182짹33% vs. 128짹61%, p=0.001). vWF-Ristocetin cofactor was increased as increasing age (r=0.253, p=0.046), left atrial size (r=0.425, p=0.017). Thrombomodulin was increased as increasing age (r=0.367, p=0.001), left atrial size (r=0.383, p=0.028) with presence of congestive heart failure (2.6짹1.4 vs. 1.7짹0.5, p=0.033). Among inflammatory markers, IL-6 was increased with diabetes mellitus (18.2짹0.4 vs. 10.9짹6.4, p<0.001). Quantitative CRP was increased as increasing age (r=0.292, p=0.017), left atrial size (r=0.486, p=0.005) and hs-CRP was increased as increasing age (r=0.354, p=0.004), left atrial size (r=0.495, p=0.005). Fibrinogen was increased as increasing age (r=0.360, p=0.002), left atrial size (r=0.517, p=0.003). Platelet activation was not considered to contribute to development of TE. Conclusion: Markers for endothelial dysfunction is considered the most powerful predictor for the development of TE in persistent and permanent AF.