In order to evaluate the exact role of GnRH agonists, we have undertaken a randomized prospective study comparing two groups of 90 normo-ovulatory patients, aged less than 38 years and with tubal infertility with no male factor. Luteinizing hormone releasing hormone analogue (DTRP6 administered in a long protocol, for at least 15 days) was associated with human menopausal gonadotrophin (HMG) induction in group I. In group II, stimulation was performed using HMG alone (three ampoules per day in general, from days 2 to 7 of the cycle). Apart from the well known results demonstrated in the literature of a reduced incidence of inadequate responses, an absence of premature luteinization and a greater number of oocytes per retrieval (8.8 +/- 4.9 versus 6.8 +/- 3.2, P less than 0.01 in group II), this study confirms the higher pregnancy rate (21.1 versus 12.2% per cycle and 24.7 versus 17.1% per oocyte retrieval, not significant) and underlines the higher plasma progesterone levels and lower E2/P ratio in group I from D - 1 to D + 5, which could explain a better maturation of the oocytes and the endometrium.