Procoagulant state, inflammation, and endothelial dysfunction have been documented in metabolic syndrome. Endothelial dysfunction is a strong predictor of cardiovascular events. Studies on the association of thrombin-activatable fibrinolysis inhibitor and thrombosis are still controversial, but substantial evidence suggests that increased thrombin-activatable fibrinolysis inhibitor or thrombi n-activatable fibrinolysis inhibits or protects against arterial thrombosis. This study aimed to assess concomitantly the effects of fenofibrate therapy on thrombi n-activatable fibrinolysis inhibitor concentrations and endothelial functions in patients with metabolic syndrome. Twenty-five patients (16 women; mean age 50.4 +/- 7.0) were enrolled in the study. Plasma thrombin-activatable fibrinolysis inhibitor, C-reactive protein, and fibrinogen levels were measured before fenofibrate administration and after 8 weeks of fenofibrate treatment. Endothelial function was assessed by endothelial-dependent flow-mediated dilatation from brachial artery. Pretreatment (baseline) thrombi n-activatable fibrinolysis inhibitor level was 52.3 (1.2-119.7) decreasing to 7.7 (0.9-51.2; P < 0.001) after 8 weeks of fibrate treatment. Endothelial functions, which were measured with flow-mediated dilatation, were significantly improved after treatment (mean flow-mediated dilatation was 6.76 +/- 2.21 at baseline and 10.66 +/- 1.17% after 8 week of fenofibrate treatment, P < 0.001). Fenofibrate decreases thrombin-activatable fibrinolysis inhibitor levels and improves endothelial function in metabolic syndrome and, thus, suggests a potential for protection against cardiovascular effects. Further studies are warranted to confirm the effects of fibrates on thrombin-activatable fibrinolysis inhibitor and for conclusive evidence on the association between thrombin-activatable fibrinolysis inhibitor and thrombosis.