Prolonged pulsatile exogenous GnRH allows differentiation between hypothalamic and pituitary causes of hypogonadotrophic hypogonadism and is able to induce ovulation and pregnancy in most of women with hypothalamic amenorrhea (HA). When compared with human menopausal gonadotropin, GnRH appears to be a more efficient therapy of HA but yields inferior results in chronic anovulatory patients with persistent LH secretion. Pulsatile GnRH following a GnRH-analog suppression represents a new promising treatment of infertile women with polycystic ovarian syndrome. However such a combined therapy is time-consuming and only permits to attempt 3 to 4 stimulated cycles during a year. Therefore the successful preliminary reports need to be confirmed by a further randomized study.