Androgen deprivation therapy (ADT) is the standard care in men with advanced prostate cancer. Continuous testosterone suppression is essential to treatment efficacy. Recently a 1 year depot compound, histrelin, (VANTAS: Orion Pharmaceuticals, Finland; Endo Pharmaceuticals, USA), a gonadotropin-releasing hormone (GnRH) analog, was approved for hormone therapy of prostate cancer. In the present study the therapeutic efficacy of this compound was investigated, in addition to its impact on testosterone values and velocity as well as PSA.