The therapeutic efficacy and safety of various doses of leuprorelin acetate depot were determined in an open, multicentre study of patients with locally advanced or metastatic prostatic cancer (stages C, D1 or D2). Patients were randomly assigned to receive 3.75 mg (30 cases), 7.5 mg (eight cases), 15 mg (eight cases) and 30 mg (one patient) leuprorelin acetate depot administered subcutaneously once every 4 weeks. Of the 43 patients evaluable, two (5%) had complete remission, 23 (53%) partial remission and 13 (30%) patients stable disease. No significant differences were observed in response rates in relation to dose, disease stage or previous hormonal therapy. Disappearance or improvement in bone pain and urinary symptoms occurred in 63% and 79% of cases, respectively. Serum androgen concentrations decreased rapidly and persistently to castration levels, without significant differences for different doses. Treatment was well tolerated with a low incidence of mild side-effects - gynaecomastia (16%), nausea/vomiting (13%) and diarrhoea (2%). It is concluded that 3.75 mg leuprorelin acetate depot given subcutaneously once every 4 weeks is able to produce hormonal effects in all patients, an overall objective response comparable to that obtained using higher doses.