We determined the effect of baicalein on prostatic hyperplasia in experimental animal models. Prostatic hyperplasia was induced by testosterone propionate in mice and castrated rats and by transplantation of homologous strain fetal mice urogenital sinus in mice. With the histopathological examination, the efficacy of baicalein on prostate hyperplasia in experimental animals was evaluated by the activity of serum acid phosphatase (ACP) and the following norm of the prostate gland: the volume, wet weight, wet weight index, dry weight index, DNA contents and prostatic epithelial height and cavity diameter. Results showed that baicalein at doses of 260 and 130 mg/kg administrated intragastrically (i.g.) significantly inhibited prostatic hyperplasia in castrated rats induced by testosterone propionate compared with the negative control group (p<0.01). Baicalein at doses of 520 and 260 mg/kg (i.g.) also significantly inhibited prostatic hyperplasia in mice induced by transplantation of homologous strain fetal mouse urogenital sinus and by testosterone propionate (p<0.01). These results suggested that baicalein has an inhibitory effect on prostatic hyperplasia in experimental animals.