Objective To investigate the effect of soybean isoflavone on histology and uhrastructure of benign prostatic hyperplasia in rats.Methods Male SD rats were injected subcutaneously testosterone propionate for 28 d to induce prostatic hyperplasia,and the rats were divided into 5 groups:control group,model group,and 3 test groups with SI in a dose of 60 mg/(kg·d),120 mg/(kg·d) and 240 mg/(kg·d),respectively.The wet prostate weight,prostatic index,morphological,uhrastmetural and morphometrie changes of the prostatic shndular and interstitial tissues were observed.Results The prostate wet weight,prostatic index and prostatic volumes in all dose groups were significantly lower than those in the models.In comparison with the model group,height of prostatic epithelial cells,glandular average diameters,volumes and surface areas in unit volume,as well as glandular circumferences,glandular relative total volumes and interstitial relative total volumes were all significantly decreased.Glandular counts,density,ratio of glandular surface area to volume,and glandular average curvature were all increased.Conclusions Soybean isoflavone can inhibit prostatic hyperplasia in rats.