Despite various interventions, the mortality rate after acute hepatic failure remains extremely high. Although it has been shown that administration of regenerating liver cytosol (RLC) after hepatic failure improves the survival rate of animals, the sequence in which various hepatic functions are altered after acute hepatic failure and their improvement by RLC remain unknown. To study this, fulminant hepatic failure in rats was produced by intraperitoneal injection of 1.5 gm/kg D-galactosamine (GAL). Twenty-four hours after 68% hepatectomy in normal rats, RLC was prepared and 4 ml of this solution (40 to 50 mg protein) was injected intraperitoneally in other animals at 6 or 24 hours after GAL administration. The long-term survival rate was 19.4% in the GAL-vehicle (control) group, 26.7% in the GAL-treated rats given liver cytosol from normal rats, and 72.2% (p < 0.01 compared with both groups) in rats given RLC even 24 hours after GAL administration. Reticuloendothelial function was depressed at 24 and 48 hours after GAL administration; however, treatment with RLC but not vehicle or normal liver cytosol at 6 or even 24 hours after GAL administration significantly improved reticuloendothelial function 24 hours after GAL administration. DNA synthesis (an indicator of cell proliferation) did not increase in any group 24 hours after GAL administration; however, it increased strikingly at 48 hours in the GAL-RLC groups. Serum bilirubin levels were also lower in the RLC group 48 hours after GAL administration. Thus RLC administration improved survival, reticuloendothelial function, DNA synthesis, and hepatocyte function after GAL-induced acute hepatic failure. Improvement of reticuloendothelial function by RLC occurred before stimulation of DNA synthesis and appears to play an important role in improving survival after hepatic failure.