A prothrombin complex concentrate was used in attempts to control life-threatening hemorrhage in 4 patients with chronic liver disease. The population manifested profuse bleeding from varices and/or hemorrhagic gastritis; 3 had Laennec's cirrhosis and 1 had postnecrotic cirrhosis from childhood hepatitis. In all patients the complex was given in amounts needed to raise the prothrombin (factor II) level to approximately 100% of normal. In all 4 cases the prothrombin time and prothrombin complex factors approached normal within 1-2 hr after beginning the infusion. In all patients bleeding ceased with correction of the clotting status. One patient rebled several hours after completing the infusion. In several patients, increases in factors V and VIII were noted following infusion of the concentrate. A further unexpected finding was a spontaneous increase in factors II and IX at 3 days postinfusion. Prothrombin complex concentrate appears to be useful in controlling the hemorrhage of chronic liver disease when used alone or in combination with other modalities to correct specific hemostatic defects; however, patients may be expected to rebleed when the effect of the concentrate wears off. Its use, therefore, should probably be restricted to those patients who are to undergo corrective surgery of the bleeding point once hemostasis is achieved.