To evaluate the effects of a traditional Chinese herbal medicine, Hochu-ekki-to [Bu-zong-yi-qi-tang], on the bone loss induced by ovariectomy in rats, ovariectomized female rats of the Sprague-Dawley strain at age 35 weeks were daily given Hochu-ekki-to and/or 17 alpha-ethynylestradiol for 8 weeks by gastric tube and, subsequently, the serum hormone levels and the tibial bone mineral density were measured. Hochu-ekki-to treatment suppressed the ovariectomy-induced reduction of the bone mineral density in the whole and metaphysis of tibia with a slight increase of serum levels of estradiol and progesterone, maintaining bone mineral density values similar to that in the estradiol treated ovariectomized rats, as well as the intact control rats. Hochu-ekki-to is suggested to elevate the serum levels of ovarian hormones slightly and prevent bone loss in ovariectomized rats.