- The benefits of combined pituitary suppression/ovarian stimulation therapy in IVF-ET programmes could be avoiding an untimely LH secretion, synchronization of the ovarian response to stimulation, an increased number of ova obtained and embryos replaced and a higher pregnancy rate. The first two advantages can be considered as direct effects of the combined therapy, while the others result, at least partly, from the more aggressive use of gonadotrophins. The capability of combined GnRH analogue/gonadotrophin treatment to avoid failures due to premature luteinization of follicles seems to be unequivocal. In order to obtain a better synchronized ovarian response to stimulation, new treatment schemes, based on prolonged use of currently available agonists or on application of potent synthetic GnRH antag onists, will have to be developed. Basic studies concerning the presence and the extent of a direct effect of GnRH analogues upon ovarian function would also help in a better understanding and more efficient application of the combined suppression/stimulation therapy in IVF—ET programmes.