Nonsteroidal antiandrogen casodex and steroidal antiandrogen epitestosterone were administered to intact male mice, and their effect on femoral bones and circulating calcium, phosphate, testosterone, and LH were compared with controls and castrated animals. Pure antiandrogen casodex in a dose used in humans for treatment of prostate cancer decreased the weight of seminal vesicles, organ which is highly sensitive to the androgenic effect, increased insignificantly the concentration of LH and of testosterone, but did not have any effect on bone density or mineral content of bone. Epitestosterone, which not only inhibits the binding of androgens to their receptors but also inhibits the formation of dihydrotestosterone from testosterone, and is reported to interfere with aromatization of testosterone to estrogens, decreased the bone density, ash weight, and calcium and phosphate content of femoral bone tissue significantly, although not to values as low as those seen in castrated animals.