Extracorporeal pig liver perfusion was adopted in 2 patients with acute hepatic coma due to fulminant hepatitis. Exchange transfusion was used in a third patient, while a fourth was subjected to both procedures. A marked haematological improvement was noted in all cases. Yet, three patients died without showing any clinical benefit. In the fourth case, coma regressed and gradual improvement to the point of complete recovery was achieved. Liver perfusion and exchange transfusion in the same patient were attended by very different clinical effects, though each procedure produced a comparable improvement at the blood chemistry data. Careful analysis of the data suggests that the difference was attributable to discrepancies between the degree of tissue purification achieved.