Luteinizing hormone-releasing hormone (LH-RH), purified from porcine hypothalami, was infused iv for 24 hours into a woman with secondary amenorrhea who was pretreated with human menopausal gonadotropin (HMG—Pergonal). Supplemental LH-RH was injected iv rapidly at 8 and 24 hours during the infusion. Ovulation, indicated by the marked rise in urinary pregnanediol levels, was confirmed by pregnancy. During a control cycle in which HMG but not LH-RH was administered, no rise in urinary pregnanediol values occurred. It is suggested that LH-RH may be useful in the treatment of some cases of infertility.