A randomized, prospective study was conducted to compare ovarian stimulation with human menopausal gonadotropin (hMG) and human follicle-stimulating hormone (hFSH) in an in vitro fertilization and embryo transfer (IVF-ET) program. Minimal inclusion criteria included age less than or equal to 37, tubal infertility, regular menstrual cycles before IVF, and a normal semen analysis. Equivalent doses (225 IU/day) of either hMG (N = 20) or hFSH (N = 20) were administered, and the patients followed by serum estradiol (E2) levels and pelvic ultrasound. Parameters related to the ovarian response to therapy, the number and quality of ova recovered, and the cycle outcome were compared in the two groups using the Student's t-test and chi-square analysis. No difference was detected between the groups in peak E2 levels (828 +/- 78 versus 819 +/- 79 in the hMG and hFSH groups, respectively), day of human chorionic gonadotropin (hCG) administration (9.3 +/- 0.3 versus 9.7 +/- 1.01), occurrence of spontaneous luteinizing hormone (LH) surge (44% versus 27%, P greater than 0.05, chi square analysis), average number of ova recovered (5.0 +/- 0.7 versus 5.6 +/- 1), ova maturation (7.5% versus 12.7% rate of immature ova), rate of normal and abnormal fertilization (9.2% versus 8.1% polyspermic fertilization), cleavage stage at transfer (3.6 +/- 0.4 versus 3.4 +/- 0.7 cells per embryos), the number of embryos transferred (2.5 +/- 0.3 versus 2.6 +/- 0.3), or the occurrence of pregnancy (1 in the hMG group and 2 in the hFSH group).(ABSTRACT TRUNCATED AT 250 WORDS)