The objective of this study was to compare, in infertile women suffering from severe hypogonadotropic amenorrhea, the therapeutic utility and the incidence of complications arising from fertility treatment by the conventional human menopausal gonadotropin/human chorionic gonadotropin (hMG-hCG) method, the hMG step-down method, the sequential hMG/gonadotropin-releasing hormone (GnRH) method and a new, modified hMG-GnRH method that has been developed by us. In the step-down method, the daily dose of hMG was decreased from 150 IU to 75 IU when the follicle diameter reached 11-13 mm. In the sequential hMG-GnRH, hMG injection was switched to pulsatile GnRH administration (20 microg/120 min SC), when the follicle diameter reached 11-13 mm. In our new modified hMG-GnRH, pulsatile GnRH was injected together with hMG. Daily hMG was stopped and the GnRH dosage was changed from 10 microg to 20 microg when the follicle diameter reached 11-13 mm. Initially, the three established methods were applied randomly to treat 34 cycles in 20 women; and subsequently, five patients who failed to conceive following treatment by sequential hMG-GnRH were then treated by the modified hMG-GnRH method. More than eight growing follicles and multiple pregnancies were observed during treatment by the conventional method. The incidence of ovarian hyperstimulation syndrome (OHSS) was 25.7% with the conventional method, 20.0% with the step-down method and 0% with the sequential hMG-GnRH method; however, the rate of ovulation was only 50% with the sequential hMG-GnRH method. By contrast, with the modified hMG-GnRH method, less than three growing follicles occurred in 81.8% of patients, there was a 100% rate of ovulation, and neither OHSS nor multiple pregnancies were observed. Moreover, the modified hMG-GnRH method induced pregnancy in 3 out of 5 patients. These data indicate that this new method is favorable for the treatment of severe hypogonadotropic amenorrhea.