Antiandrogens interfere with androgen action at the target organ. They vary in structure and mode of action and either block enzyme reactions thereby limiting the formation of potent androgens or specifically block the androgen receptor; some anti- androgens affect both enzyme reactions and androgen receptor. A female foetus in utero is at risk of developing feminized external genitalia if his mother is having treatment with an antiandrogen. Concurrent use of adequate contraception is therefore an essential component of any treatment regime using an antiandrogen. Additionally most antiandrogens have various side effects, some of which are potentially dangerous. Consideration of the risk/benefit ratio is therefore of utmost importance in choosing anti-androgen drug, as the underlying condition, however distressing, is benign.