We have partially purified hepatocyte stimulator peptide (HSP) from liver of human fetus. Immunizing BALB/C mice with crude HSP, we obtained finally 2 antibody-producing colonies, which produced IgG3 and IgG1 revealing clearly the dose dependent inhibitive activity for HSP. Determining the serum HSP and TNF in patients with fulminant hepatic failure, we found that patients with higher HSP/TNF ratio had better prognosis than those with lower ratios. By linking anti-HSP with activated agarose gel, an anti-HSP-sepharose 4B affinity chromatographic column was developed for the isolation of HSP from crude HSP. The result from SDS-PAGE of isolated HSP shows that its molecular weight is about 17.5 KD. Furthermore, HSP has strong growth stimulatory activity for hepatocyte and initiates the DNA synthesis of hepatocyte in vitro. It is not a heparin-binding growth factor and its biological activity is not potentiated by heparin. It is stable at 95 degrees C or pH 2-12 and resistant to 0.25% trypsin digestion for 60 min. These characteristics indicated that HSP might be a novel hepatocyte growth factor and be used in clinical therapy for fulminant hepatic failure and infectious shock. Further study is needed in this respect.