A regime for therapeutic management of a benign prostatic hyperplasia and prostatic cancer employs Cetrorelix alone or in combination with .alpha.-reductase inhibitors or .alpha.-receptor blocking agents. The regimen reduces the volume of the prostate and avoids the side effects associated with testosterone levels being in a castration range. Cetrorelix is administered at dosages between 0.5 mg/day and 20 mg/week or about 0.014 mg/kg body weight per day to 0.30 mg/kg body weight per week or at levels of about 25 to 120 mg of Cetrorelix per month or 0.376 mg/kg to 1.71 mg/kg per month. Cetrorelix can be administered with .alpha.-reductase inhibitors or .alpha.-receptor blocking agents.