Cyproterone acetate is a steroidal anti-androgen that blocks the androgen-receptor interaction and reduces serum testosterone through its weak anti-gonadotropic action. It can be regarded as the only anti-hormone that causes complete androgen blockade as monotherapy. Many animal experiments and several clinical phase II and phase III trials have demonstrated that it deserves a place in the endocrine therapy of advanced prostate cancer, particularly for those patients who find orchidectomy unacceptable and who do not have known cardiovascular risks. Additionally, cyproterone acetate can be used safely to prevent disease flare when a luteinizing hormone releasing hormone analog is the drug of choice and to suppress hot flashes in response to LHRH agonists or after orchidectomy.