Five patients with primary hypogonadotrophic amenorrhea were treated for the induction of ovulation with I.V. pulsatile Gn-Rh doses ranging from 2.5 to 12.5 micrograms/90 min) for 15 cycles. Ovulation occurred during Gn-Rh treatment in 7 cycles (A) or after i.m. HGC administration (5,000-10,000 IU) (B = 6) (ovulation rate = 86%). Four pregnancies (A = 2; B = 2) were obtained (in one case there was a twin pregnancy). Echographic and endocrine patterns were evaluated. Ovulatory follicular diameter was 18.3 +/- 6.0 mm, no difference between A and B (21.8 +/- 5.6 and 16.0 +/- 5.1 mm, respectively) was observed. In addition E2 preovulatary plasma levels were similar in the two groups examined (334 +/- 131 and 300 +/- 89 pg/ml, respectively). Also endocrine and echographic profiles of conceptive (C) and non conceptive (NC) cycles were similar. Furthermore all doses resulted effective in determining the ovarian response and no difference was found at different dosage used. It is concluded that pulsatile GnRh is a "physiological" way of inducing ovulation in PHA patients. By analysis of the present data we consider it advisable to induce ovulation by the enhancement of the endogenous LH peak which occurs during Gn-Rh administration (A group) and then periodic injections of HCG can be used for maintaining the luteal function.