Pulsatile GnRH therapy is indicated for men with inborn hypothalamic hypogonadotropic hypogonadism and those with acquired gonadotropin deficiency due to hypothalamic disfunction. Oligospermia with hypothalamic GnRH deficiency is a rare indication for efficient GnRH therapy. Based on extended own experience and on the experience of numerous other groups, pulsatile GnRH therapy should be administered as follows: Onset of therapy should not start before the 16th year of age with clearly diagnosed delayed pubertal development. Subcutaneous administration of GnRH is preferred. The cannula should be changed every other day. Injection solutions should not contain Heparin. For diagnostic use or for inefficient subcutaneous therapy, continuation of intravenous therapy containing Heparin in the solution is recommended. The dosage should be measured on the increase of testosterone with stepwise increase of GnRH (25-200 ng/kg/pulse; 2.5-20 micrograms/pulse). As a pulse interval, 120 minutes appeared to be the most efficient, however 90 minutes of pulse intervals may also be efficient. The duration of therapy should be at least three months controlled on the testosterone level, the testes' volume and later on the sperm count.