Changes in the fibrinolytic system may lead to coagulation disorders in acute trauma patients. This study examined fibrin degradation by measuring D-dimer crosslinked fibrin degradation products (indicates hypercoagulability), plasminogen activators (fibrinolysis), and antithrombin III in 42 adult trauma patients and correlated these data with injury severity, types of injury, complications, and clinical tests of coagulation. Hypercoagulability and suppression of fibrinolysis were seen in most patients and were not correlated with severity of injury. These changes appeared most severe in patients with nervous system injury. Several patients with less severe injuries but evidence of hypercoagulability developed clinical evidence of pathologic thrombosis. Latex agglutination of D-dimer provides a rapid test of fibrinolysis that may be clinically useful in the management of trauma patients who cannot be easily studied for thrombosis.