A study was carried out in 30 male patients with benign prostate hyperplasia to assess the effectiveness of treatment with a progestational agent, gestonorone caproate (200 mg), given intramucularly every 7 days over a period of 2 to 3 months. The results showed definite subjective and objective improvement after treatment. Residual urine determination diminished significantly after therapy in 78% of the cases completing the study; uroflometry also showed improvement. There appeared to be some reduction in the degree of occlusion of the urethral lumen in at least 13(65%) out of 20 patients given follow-up cystopanendoscopy after 6 months. This result was further supported by improvement in urinary flow rates and uroflometrograms in the same patients. The only adverse effect of treatment noted was the development of impotency in 21 patients.