The aim of the present study is to validate the effects of treatment with different concentration of estrogen receptor alpha agonist, propyl pyrazole triol (PPT) on the weight and histological structure in the accessory reproductive organs (ventral prostate, seminal vesicle and preputial gland) of male mouse. Treated groups received different doses of PPT 0.01 mg, 0.1 mg and 1.0 mg per week respectively, for 3, 5, and 8 weeks. In general, the weight of reproductive organs was increased in PPT 0.01 mg and 0.1 mg treatment, however decreased in PPT 1.0 mg treatment. Epithelial tissues in the ventral prostate were changed from simple columnar epithelium to squamous or cuboidal epithelium in the treated groups. On week 3, PPT groups caused decrease of epithelial cell height in the ventral prostate. Lumen of the seminal vesicle was narrowed in the treated group. Epithelial cell height of seminal vesicle was reduced in the PPT treatment. Acinus tissue of preputial gland in PPT 1.0 mg treatment was dramatically atrophied than that of control group. These results are useful as a reference to determine the administration concentration of PPT in experiments for understanding the physiological functions of estrogen in the male.