Background: Renin-angiotensin-aldosterone system has been reported to influence prothrombotic and hypercoagulable state in atrial fibrillation (AF). However, it is not certain whether combination therapy with angiotensin converting enzyme inhibitor (ACEI) and angiotensin receptor blocker (ARB) may have additive benefit for the improvement of endothelial dysfunction and prothrombotic condition and reduce thromboembolism (TE) in patients with persistent and permanent atrial fibrillation. Subjects and Methods: All patients had more than 1 risk factor for TE and were divided into 3 groups. Group I (n=57, M:F=36:21, 59짹11 years) was treated with only ACEI, group II (n=43, M:F=22:21, 59짹10 years) with only ARB, group III with combination of ACEI and ARB (n=46, M:F=26:20, 57짹11 years). Markers for endothelial function (von-Willebrand factor, vWF; factor 8 related antigen), inflammation [WBCs, ESR, quantitative and high sensitivity C-reactive protein (CRP)] and coagulation system (fibrinogen, fibrinogen degradation product, fibrin d-dimer) were measured at baseline state and at 6 month follow-up. Antithrombotic therapy was done in all patients according to ACC/AHA guideline. Results: The TE did not occur in all groups during 6 month follow-up. There were no significant differences in levels of each marker at baseline state. vWF-factor 8 related antigen was significantly reduced at 6 month in group I (161짹41% vs. 133짹44%, p=0.023) and group III (162짹45% vs. 132짹54%, p=0.034) but not in group II (158짹48% vs. 147짹53%, p=0.227). Fibrinogen was significantly reduced at 6 month follow-up in group I (338짹88 vs. 273짹82%, p=0.008) and group III (332짹87 vs. 277짹80, p=0.002) but not in group II (328짹87 vs. 298짹83, p=0.162). Markers for inflammation were not changed significantly in all groups. Conclusion: ACEI was better than ARB for the improvement of endothelial dysfunction in persistent and permanent atrial fibrillation and combination therapy had little additive effect on endothelial function.