Benign prostatic hypertrophy, a common ailment among elderly men, usually is treated by surgery. Since androgens enhance prostatic hypertrophy, their withdrawal seems a logical way to treat this condition. Recently gonadotropin-releasing hormone analogues, known to produce "chemical castration," have been tried in cases of benign prostatic hypertrophy. We report our experience with 20 men treated by a monthly injection of gonadotropin-releasing hormone for prolonged periods. In 17 men treated for 6 months the prostatic volume decreased to an average of 63% of the initial volume; however, this did not correlate with clinical objective improvement. Only 6 men attained normal flow rates. Residual urine volume remained unaltered. Ten patients experienced subjective amelioration, while only 7 (40%) reported objective and subjective improvement. Maximal decrease in prostatic volumes was reached at 9 months of treatment and further treatment did not cause additional shrinkage. At 3 months after discontinuation of treatment prostatic volumes returned to 95 +/- 10.5% of pre-treatment values. A similar decrease in flow rates also was noted. Symptoms remained improved for longer periods. We conclude that this mode of treatment offers little to the majority of men with benign prostatic hypertrophy. Proper patient selection, based perhaps on serum prostate specific antigen, might augment positive results. This therapy should be restricted to patients considered high risk for any surgical and anesthetic intervention, and then it will have to be continued indefinitely.