The effects of pulsatile GnRH therapy have been studied for the treatment of different forms of hypogonadotropic hypogonadism, including idiopathic hypogonadotropic hypogonadism and hypogonadism developed as a result of treatment with combination of surgery and irradiation for pituitary or hypothalamic tumor. GnRH was administered subcutaneously in a dose of $10{mu}g$ every 2 hours with the pulsatile infusion pump. With GnRH therapy, all patients improved secretion of LH, FSH and testosterone. Testicular volumes increased. Spermatogenesis was induced in 8 patients. Pulsatile GnRH therapy is an effective treatment for idiopathic hypogonadotropic hypogonadism and can have a role in hypogonadism previously treated with combination of surgery and irradiation for pituitary or hypothalamic tumor.