The effect of the deleted form of hepatocyte growth factor (dHGF) on thrombopoiesis was studied in rats. When normal rats were injected with dHGF (0.5 mg/kg i.v. twice a day), the number of platelets increased to about 1.5-fold the initial level. In addition, the treatment with dHGF (0.5 mg/kg i.v. twice daily) significantly increased the number of platelets in rats with liver cirrhosis induced by carbon tetrachloride and phenobarbital. When dHGF was given to rats at a dose of 0.05 or 0.5 mg/kg from the beginning of the induction of dimethylnitrosamine liver cirrhosis to day 28, dHGF dose-dependently ameliorated thrombocytopenia and completely prevented it at a dose of 0.5 mg/kg. These results indicate that dHGF may be applicable to the treatment of thrombocytopenia associated with liver cirrhosis.