It is well known that prognosis is very poor in patients with severe hepatic insufficiency such as congenital biliary atresia and fulminant hepatitis. The liver transplantation is only effective therapy for these patients and living-related liver transplantation is becoming popular in Japan. We observed the changes in serum human hepatocyte growth factor (h-HGF) levels of the recipients during the operation in 3 cases of congenital atresis and one of fulminant hepatitis. Serum h-HGF values in these patients reached the maximal levels (5-10-fold compared to the base line values) at the phase of portal or hepatic artery anastomosis during the operation. These observations suggest that the increase of h-HGF in the recipient is derived from the following three origins. (1) Wash outed h-HGF from the liver of the donor. (2) Induced h-HGF from other organs than the liver of the recipient. (3) The decreased catabolism of h-HGF in recipient due to total hepatectomy.