In a retrospective international study 223 pregnancies induced with pulsatile hormone-releasing hormone (LH-RH) were evaluated. In patients with hypothalamic amenorrhea (HA) and polycystic ovarian disease (PCOD) the abortion rate was similar (10% vs 8.7%). The premature delivery rate was significantly higher, however, in the patients with HA, but this could be explained by the higher incidence of multiple pregnancies in this group. Thirty multiple pregnancies were observed in the HA group (n = 174) compared with none in the PCOD group (n = 24; p less than 0.05). The incidence of multiple pregnancies in the HA group correlated to the pulse dose (p less than 0.05). The 1st treatment cycle resulted in more multiple pregnancies than did subsequent cycles (p less than 0.05). Difference in pulse interval did not affect the incidence of multiple pregnancies, nor did the route of administration (intravenous or subcutaneous). The incidence of congenital anomalies was comparable to that with spontaneously achieved pregnancies.