Plasma cross-circulation which resembles plasma exchange clinically was carried out in between galactosamine (GalN) treated hepatic failure rats and normal rats. Twenty-four hours after the injection of GalN, plasma cross-circulation was performed at a plasma flow rate of 0.1 ml/min for 6 hours. In eighteen hours after the completion of a procedure, survival rate was 75% (6 out of 8 survived) in GalN injected rats treated with plasma cross-circulation, as compared to 40% (4 out of 10 survived) in GalN injected rats treated with sham-circulation. State 3 oxygen consumption and ATP synthesis in the liver mitochondrial respiratory function, and ATP and total adenine nucleotide contents in the liver in the former group were significantly higher than those in the latter group at the time of sacrifice of the survived animals. These appear to suggest that plasma cross-circulation enhances mitochondrial phosphorylative activity in the liver and may contribute higher survival rate of the rats. Plasma exchange using a large amount of fresh plasma, therefore, would be effective for the treatment of acute liver failure in its early stage.