Detailed coagulation studies were performed in a group of 19 patients with primary hepatocellular cancer (PHC) and the results were compared statistically with the findings in 19 control subjects. Various funcitonal and immunochemical methods were employed in determining the possible presence of functional or structural coagulant protein abnormalities. The patient group was characterized by prolonged prothrombin times, partial thromboplastin times, and Reptilase times, increased levels of fibrinogen, factor VIII, and factor VIII-related antigen, moderately devreased levels of factor V, factor IX, factor X, antithrombin III, and plasminogen, and reduced levels of factor II and factor VII. Functional, immunochemical, and biochemical analysis failed to detect the presence of acquired protein abnormalities. These findings indicate that hemostatic changes in primary hepatocellular cancer are nonspecific in character. Severe alterations in the plasma levels of one or more of these hemostatic factors may occur.