In 11 patients with hepatic coma (stage IV and V according to Abouna) extracorporeal haemoperfusion using the Scribner shunt (radial or profunda femoris artery) was performed over 12 to 27 hours with 22 baboon and one human livers. Eight patients emerged from coma, six of them showed sufficient regeneration of the diseased liver. Four patients were discharged as cured, one patient died of acute pancreatic necrosis, a further one due to bleeding from an old gastric ulcer. In the 2 remaining patients the coma recurred within 48 hours. Tree patients never came round from coma. After perfusion no antibodies against baboon proteins were demonstrable in the patients. Thus there is very little danger of an anaphylactic reaction when perfusion is repeated. The titre of preformed cytotoxic antibodies against baboon cells in patients' serum rises only after 1-2 weeks and decreases again after 4 weeks. In our experience extracorporeal liver perfusion with baboon or human livers is the most promising method for treatment of hepatic coma.