To investigate the pathogenesis of fibrinolysis in liver disease, antithrombin III (AT III) activity, prothrombin fragment (F1 + 2) and d-dimer (D-DI) were measured in 50 patients with liver disease and in 17 healthy controls. Moreover, 4 patients with cirrhosis were randomly assigned to receive either an intravenous infusion of AT III (at two different dosages) or placebo, with a crossover design. Increased levels of D-DI were detected in patients with cirrhosis and hepatocellular carcinoma in comparison both with control subjects and with patients with acute hepatitis or mild chronic liver disease. An inverse correlation was observed between AT III and D-DI (r = -0.755, P < 0.001, simple linear regression), while no correlation was found between D-DI or AT III and F1 + 2. The correlation of the deficiency of AT III activity by infusion of human AT III did not result in any significant change (P0.10, analysis of variance for repeated measures) of the plasma concentration of either D-DI or F1 + 2, in comparison to placebo. Thus, advanced forms of chronic liver disease, but not acute hepatitis and mild forms of chronic liver disease, are associated with increased plasma concentrations of markers of fibrinolysis, which are inversely correlated with AT III activity. However, the correction of the deficient AT III activity does not affect the plasma concentration of either D-DI or F1 + 2, thence not supporting the hypothesis that enhanced fibrinolysis in advanced liver disease is the result of low-grade disseminated intravascular coagulation.