The authors evaluated elements of the coagulation and fibrinolytic systems in 18 male patients with intermittent claudication vs 19 men matched for risk factors who served as controls. Prothrombin time and activated partial thromboplastin time did not significantly differ in the patients and the controls. The plasminogen level in the two groups was not significantly different. The level of lipoprotein(a) was significantly higher in the patients than in the controls. The levels of antigen and the activity of protein C did not differ significantly between the two groups. The thrombomodulin level was significantly higher in the patients than in the controls. There were no significant differences between the two groups in the levels of alpha 2-macroglobulin, C1-inactivator, or antithrombin III. The levels of fibrinogen and alpha 1-antitrypsin were significantly higher in the patients vs the controls. Significantly lower levels of alpha 2-plasmin inhibitor and higher levels of alpha 2-plasmin inhibitor/plasmin complex and thrombin/antithrombin III complex were found in the patients vs the controls. These findings suggest that the levels of thrombin/antithrombin III complex, alpha 2-plasmin inhibitor/plasmin complex, and thrombomodulin may perhaps serve as indicators for injury to the peripheral endothelium and that the coagulation and fibrinolytic systems may be activated in patients with intermittent claudication.