The addition of the gonadotropin releasing hormone (GnRH) agonist Buserelin to human menopausal gonadotrophin/human chorionic gonadotropin (HMG/HCG) during ovarian stimulation was evaluated in 23 cycles of 21 women who previously had unsuccessful IVF treatments when stimulated with clomiphene--HMG/HCG. No adverse effects of GnRH-agonist on folliculogenesis were seen. A mean number of 7.2 oocytes per retrieval was collected in 20 treatment cycles. Oocytes quality, fertilization and cleavage parameters were normal. Replacements by gamete intra-Fallopian transfer (GIFT) or IVF took place for 16 patients. Four patients became pregnant in their treatment cycle, one aborted. For 8 patients 18 embryos were cryopreserved, one transfer of a frozen--thawed embryo in a subsequent natural cycle led to a pregnancy. Inadequate luteal phases were constantly observed when supplementation was omitted. Further study is required to confirm that systematic luteal support improves the pregnancy rate.