The effects of 8-hour haemoperfusion through an activated charcoal column on fulminant hepatic failure were assessed in 10 dogs. The survival in the perfused animals was significantly prolonged and the onset of liver encephalopathy was markedly delayed compared to the controls. Significant decrease in plasma bilirubin and total plasma phenols was found in the perfused group. No other laboratory changes due to haemoperfusion were found. The charcoal column retained its adsorptive capability throughout the experiment as judged from phenol clearance values. In spite of current scepticism regarding its clinical use, further trials with haemoperfusion in acute liver failure seem to be warranted.