Abstract: Benign prostatic hyperplasia (BPH) in male humans is treated by administering to a male patient in which such condition has been diagnosed, an effective BPH treating amount within the range of from 1 ng to 80 mg of melatonin, which may be in the form of a pharmaceutical formulation for use in treating BPH, which comprises, in combination a carrier, diluent or adjuvant, (1) an effective BPH treating amount of melatonin; and optionally (2) antiandrogens, antiestrogens, growth hormones and/or inhibitors of prostatal testosterone reductase; and/or (3) oxazepam or other melatonin receptor profile modifier.