Steroidal antiandrogen epitestosterone was administered to intact male mice and its effect on seminal vesicles, kidney, femoral bones and circulating calcium, phosphate, testosterone and LH were compared with controls and castrated animals. Epitestosterone was previously reported as an inhibitor the binding of androgens to their receptors, an inhibitor of the formation of dihydrotestosterone from testosterone and a modulator of estradiol-estrone conversion. In the present study it is demonstrated that it decreased the weight of kidney, seminal vesicles and bone density, ash weight and calcium and phosphate content of femoral bone tissue significantly, although not to the values as low as those seen in castrated animals. Thus in mice epitestosterone effects could be classified as antiandrogenic.