D-Trp-6-LH-RH, a long acting LH-RH agonist was given in a phase II trial to 85 patients aged 52 to 88 (mean 69) with advanced prostatic carcinoma, stage B (8 pts), C (9 pts) and D (68 pts). Twenty-five patients were previously untreated, 40 had received previous hormonal therapy but none was considered has having hormone resistant tumor; 20 patients had received surgery or radiotherapy or both. D-Trp-6-LH-RH was given s.c. at a daily dose of 500 micrograms during the first seven days, followed by 100 micrograms daily. Antitumor activity was assessed after 90 days and treatment was continued in responders. The results were the following: plasmatic levels of LH were sharply decreased and those of testosterone were in all cases under 1 ng/ml by the 90th day of treatment; urinary symptoms and bone pain disappeared or were greatly improved in almost all patients; the volume of the prostate measured by ultrasonography and/or computerized tomography regressed by more than 50% of initial volume in 44% of the 34 patients for which this parameter was evaluable; bone scintiscans were improved in 18% of evaluable patients; plasmatic levels of prostatic acid phosphatases determined by radio immuno-assay were elevated in 28 patients, 61% of which presented a decrease superior to 50% or normalisation of this parameter. No disease flare up was observed on initiation of therapy. Impotence was constant but reversible on discontinuation of therapy. No other side effect could be attributed to therapy.