Serum hepatocyte growth factor (HGF) levels in patients with acute hepatic failure has been reported to increase. However, possible mechanisms responsible for HGF elevation in this syndrome remains to be determined. To explore the possible mechanisms, we measured serum HGF in patients with acute hepatic failure and self-limited acute hepatitis, using an immunoradiometric assay. Serum HGF levels in acute hepatic failure were 36-fold higher compared with those in acute hepatitis. Serum HGF values in acute hepatitis were significantly correlated with serum bilirubin and gamma-GTP levels, whereas those in acute hepatic failure were not. These clinical findings suggest that serum HGF levels in acute hepatic failure may be regulated by different mechanisms from those in self-limited acute hepatitis.