An extract from corn germ induced a positive response in the pigeon crop sack test, used for the detection of prolactin-like substances. One of the substances extracted was identified as ferulic acid, which was reported to affect serum gonadotropin levels in ovariectomized male rats. To evaluate the effects of ferulic acid on bone loss, ovariectomized female rats of the Sprague-Dawley strain at age 35 weeks were given ferulic acid and/or 17a-ethynylestradiol daily for 8 weeks, and serum hormone levels and tibial bone mineral density were measured. In metaphysis of the tibia, which was abundant in cancellous bone and more reflective of BMD than whole tibia, the BMD was markedly reduced by ovariectomy and enhanced by the treatment with estrogen or ferulic acid in the ovariectomized rats. The treatment slightly increased the serum levels of estrogen and progesterone and alkaline phosphatase activity, which was reduced by estrogentreatment, i.e. the mechanism of bone formation by ferulic acid was suggested to be different from that by estrogens. These results indicate that ferulic acid promotes bone remodeling, leading to a predominantly osteoblastic phase, besides bone resorption by osteoclasts.