The effect of human hepatocyte growth factor on the proliferation of intrasplenically transplanted hepatocytes was investigated. A human hepatocyte growth factor (360 micrograms/kg BW) was administered intravenously every 24 hr for 5 days following hepatocyte transplantation in rats. A significant increase in hepatocyte proliferation was observed morphologically and immunohistochemically (p < 0.05). The bromodexyuridine labeling index was significantly greater in human hepatocyte growth factor treated rats than in the control rats (p < 0.05). Hepatocyte growth factor may promote the proliferation of intrasplenically transplanted hepatocytes.