Dysfibrinogenemia in 36 patients with primary hepatocarcinoma and in 25 patients with cirrhosis of the liver was studied by means of reptilase time, thrombin coagulase time, fibrin polymerization and fibrinogen assays. Both groups of patients were similar in age, sex and incidence of HBs Ag. No electrolyte or fluid imbalances were present. Prolonged reptilase time and prolonged polymerization time were found in both groups; however, thrombin coagulase time was prolonged in 80% of the hepatocarcinoma group, but was normal in almost all patients with cirrhosis (p less than 0.001). In the hepatocarcinoma group, a difference of more than 100 mg per 100 ml was present between the immunologic and coagulative methods of fibrinogen determination in 36.1% of the cases, but in the cirrhotic group this difference was not present in any of the patients (p less than 0.01). We also found that by simply measuring fibrinogen levels by the Mancini method, we could distinguish hepatocarcinoma from cirrhosis in most cases.