Soluble fibrin monomer complexes (SFMC) have been quantitated in 18 patients with liver cirrhosis by means of plasma gel filtration on an agarose column. The concentration of SFMC (as related to total fibrinogen) was increased in cirrhotic patients. The difference between controls and patients, as well as the difference between compensated and decompensated cirrhotic subjects, was statistically significant. Although these data, together with the results of heparin administration in one reported case, suggest intravascular coagulation, some alternative explanations should also be considered.