The success of IVF is related to the number and quality of embryos transferred. In our IVF program we have used two different protocols for superovulation induction. In this study a group of 35 patients was randomized into two groups; the first group (15 patients) was treated with pure FSH and hMG, in the other (20 patients) the normal pituitary function was inhibited with Buserelin before the stimulation with hMG. Ovarian stimulation was monitored by ultrasound examination and endocrine parameters. The RIA determination of 17-beta estradiol (17-E2) plasmatic levels is one of the most widely used techniques in IVF cycle monitoring; however many serious disadvantages are connected with the use of RIA (short half-life of the reagents; hazard of handling radioactive materials; frequent venipunctures for the patients). For these reasons, we propose a chemiluminescence immuno assay (LIA) method for the measurement of glucuronometabolites of 17-E2 and progesterone in early morning urine samples: this technique allows to follow hormonal levels for all the cycle, avoiding patient discomfort. We have found a highly significant correlation between serum and urinary hormonal values. We noted a marked variability in the individual estrogenic response and a significant difference in the response of the two groups. The mean peak on hCG administration day was 6.4 +/- 3.5 micrograms/h for urinary E1-3G and 1270 +/- 678 pg/ml for 17-E2 in Buserelin-hMG group: these hormonal levels appear lower than without ovarian desensitization; (in FSH-hMG group we have, on the same day, 9.7 +/- 3.2 micrograms/h for E1-3G and 1630 +/- 730 pg/ml for serum 17-E2).(ABSTRACT TRUNCATED AT 250 WORDS)