Massive necrosis of the liver in acute hepatitis is frequently followed by regeneration of hepatic cells. Life is threatened during the destructive phase. With the theory that exchange transfusion might support life until regenerating liver cells resume function, the procedure was used in seven comatose patients. Three regained consciousness and two became long-term survivors. In two additional cases the exchange produced apparent improvement but the patient died. The cause of death in one was cerebral ischemia sustained during an apneic episode, and in the second case death was due to septicemia and septic shock from an infected surgical wound. Exchange transfusion did not affect the fatal course in two patients. The measurable biochemical changes consisted of reduction in levels of serum bilirubin, alkaline phosphatase, and transaminase and prothrombin time.