The study was designed to evaluate the effects of a traditional Chinese herbal medicine Hochu-ekki-to (Bu-zong-yi-qi-tang), which was composed of 10 herbal medicines and had been used for the treatment of oligospermia and as a postoperative medication in Japan, on bone loss in rats treated with a gonadotropin-releasing hormone (GnRH) agonist. Female rats at 40 weeks of age were divided into 4 groups of 8 rats each. In the three experimental groups, each animal received subcutaneous injections of the long-acting GnRH agonist, buserelin acetate, once every four weeks throughout the experiment. Beginning at 48 weeks of age, the experimental groups were given diets containing conjugated estrogens or Hochu-ekki-to for 8 weeks. The administration of the GnRH agonist reduced the bone mineral density in the whole femur to 91. 0% of that in the control group. However, administration of conjugated estrogens and Hochu-ekki-to increased the serum concentrations of estradiol 16 VSports手机版. 8- and 5. 3-fold respectively compared with concentrations in the GnRH agonist-treated group, resulting in the augmentation of the bone mineral density to 110. 3% and 106. 2% respectively. These findings indicate that Hochu-ekki-to enhances the reduced bone mineral density and causes a slight elevation of the serum estradiol levels in the chemically castrated rats. .