['The aim of this study was to investigate whether risk factors for embolism would promote thrombus formation in patients with nonvalvular atrial fibrillation (NVAF).', 'Hemostatic markers for platelet activity (ie, platelet factor-4 and beta-thromboglobulin [TG]), thrombotic status (ie, prothombin fragments 1 and 2), and fibrinolytic status (ie, d-dimer) were determined in 246 patients with NVAF (mean age, 66.1 years) and 111 control subjects without NVAF (68.3 years).', 'The beta-TG level was higher in NVAF patients than in control subjects. D-dimer levels were higher in NVAF patients having risk factors (mean [+/- SE] d-dimer level, 158.6 +/- 9.2 ng/mL) than in those without risk factors (mean d-dimer level, 92.1 +/- 6.7 ng/mL; p < 0.01) and in control subjects (mean d-dimer level: control subjects with risk factors, 79.1 +/- 10.3 ng/mL; control subjects without risk factors, 31.0 +/- 7.4 ng/mL; p < 0.01). NVAF (odds ratio [OR], 3.94; 95% confidence interval [CI], 1.87 to 8.30; p = 0.0003) and age of >/= 75 years (OR, 5.68; 95% CI, 2.87 to 11.23; p < 0.0001) emerged as predictors of elevated levels of d-dimer, and only NVAF (OR, 10.30; 95% CI, 5.67 to 18.72; p < 0.0001) emerged as a predictor of elevated levels of beta-TG.'] Is prothrombotic activity increased in patients with nonvalvular atrial fibrillation and risk factors for embolism?