The effect of liver hydrolysate (LH) derived from bovine liver on rat liver regeneration after partial hepatectomy (PH) were investigated. Oral administration of LH increased rat liver weight dose-dependently at 24 h after PH. Hepatic ornithine decarboxylase (ODC) activity and proliferating cell nuclear antigen (PCNA) labeling index were measured in regenerating rat liver as markers of cell proliferation. ODC activities at 4 and 24 h after PH were significantly increased by LH administration. PCNA labeling index at 24 h after PH were also increased by LH administration. These results suggest that LH stimulates liver regeneration in partially hepatectomized rats.