An LHRH agonist, Zoladex, was employed as a monthly depot in 56 previously untreated patients with advanced carcinoma of the prostate. Of 53 evaluable patients, 27 achieved partial remission and 7 were stable. Median duration of response was 10 months. A favorable subjective response was attained in 68% of the patients. During treatment, serum testosterone was in the castrate range in all patients except five. Possible explanations for this escape phenomenon are discussed. No toxicity was observed and treatment was well tolerated in all patients. Thirty-two patients underwent bilateral orchiectomy following treatment failure of Zoladex. In one patient partial remission according to protocol criteria was recorded. Treatment with LHRH agonists seems safe and may serve as an alternative to conventional hormonal treatment of advanced carcinoma of the prostate.