Changes in the serum concentration of hepatocyte growth factor (HGF), a potent mitogen for hepatocytes, were investigated in adult-to-adult living-donor liver transplantation (LDLT) in which liver regeneration is involved. Between August 2000 and November 2002, 15 consecutive adult-to-adult LDLTs were performed using the right lobe graft. The recipients were divided into two groups: acute liver failure (n=6) and chronic liver failure (n=9). In addition, right lobe donors (n=12) were evaluated. Measurement of HGF was performed on preoperative and postoperative days 1, 3, 7, and 14 after LDLT. The pretransplant levels of serum HGF were higher in the acute liver failure group than in the chronic liver failure group (P<0.05). After liver replacement, serum HGF levels normalized rapidly in both groups and remained rather low. Despite vigorous liver regeneration in all groups, serum HGF levels did not change significantly after adult-to-adult LDLT with right lobe graft.