Background: Elevated coagulative molecular markers could reflect the prothromb otic state in the cardiovascular system of patients with non-valvular atrial fi brillation(NVAF). A prospective, cooperative study was conducted to determine wh ether levels of coagulative markers alone or in combination with clinical risk f actors could predict subsequent thromboembolic events in patients with NVAF. Met hods: Coagulative markers of prothrombin fragment 1 +2, D-dimer, platelet fact or 4, and β-thromboglobulin were determined at the enrollment in the prospecti ve study. Results: Of 509 patients with NVAF(mean age, 66.6±10.3 years), 263 pa tients were treated with warfarin(mean international normalized ratio, 1.86), an d 163 patients, with antiplatelet drugs. During an average follow-up period of 2.0 years, 31 thromboembolic events occurred. Event-free survival was significa ntly better in patients with D-dimer level< 150 ng/ml than in those with D-dim er level ≥150 ng/ml. Other coagulative markers, however, did not predict thromb oembolic events. Age(≥75 years), cardiomyopathies, and prior stroke or transien t ischemic attack were independent, clinical risk factors for thromboembolism. T hromboembolic risk in patients without the clinical risk factors was quite low(0 .7%/year) when D-dimer was< 150 ng/ml, but not low(3.8%/year) when D-dimer w as ≥150 ng/ml. It was > 5%/year in patients with the risk factors regardless o f D-dimer levels. This was also true when analyses were confined to patients tr eated with warfarin. Conclusions: D-dimer level in combination with clinical ri sk factors could effectively predict subsequent thromboembolic events in patient s with NVAF even when treated with warfarin. Background: Elevated coagulative molecular markers could reflect the prothrombotic state in the cardiovascular system of patients with non-valvular atrial fi brillation (NVAF). A prospective, cooperative study was conducted to determine wh ether levels of coagulative markers alone or in combination with clinical Risk factors for subsequent thromboembolic events in patients with NVAF. Met hods: Coagulative markers of prothrombin fragment 1 +2, D-dimer, platelet fact or 4, and β-thromboglobulin were determined in the enrollment in the prospecti ve study. Results : Of 509 patients with NVAF (mean age, 66.6 ± 10.3 years), 263 pa tients were treated with warfarin (mean international normalized ratio, 1.86), an d 163 patients, with antiplatelet drugs. During an average follow-up period of 2.0 years, 31 thromboembolic events occurred. Event-free survival was significantly better than in patients with D-dimer level <150 ng / ml than in those with D-dim er level ≥ 150 ng / ml. Other coagulativ e markers, however, did not predict thromboembolic events. Age (≥75 years), cardiomyopathies, and prior stroke or transien ischemic attack were independent, clinical risk factors for thromboembolism. T hromboembolic risk in patients without the clinical risk factors was quite hour (0 .7% / year) when D-dimer was <150 ng / ml but not low (3.8% / year) when D-dimer w as> 150 ng / ml. with the risk factors regardless of D-dimer levels. This was also true when analyzes were confined to patients tr eated with warfarin. Conclusions: D-dimer level in combination with clinical ri sk factors could predict predict subsequent thromboembolic events in patient s with NVAF even when treated with warfarin.