Predicting ovarian response to stimulation constitutes a pivotal task in the organization of a successful in-vitro fertilization (IVF) programme. The purpose of the current study was to determine whether a new ovarian reserve test, the exogenous follicle stimulating hormone ovarian reserve test (EFORT), could improve the predictive value of the classical follicle stimulating hormone (FSH) measurements on cycle day 3 of ovarian stimulation regarding results of IVF. In this prospective study, 52 IVF candidates aged 27-42 years underwent 52 consecutive IVF cycles. These women received 300 IU of purified FSH i.m. on cycle day 3. Blood samples were taken just before the injection to measure plasma FSH and oestradiol; 24 h later, plasma oestradiol concentration was determined. Two menstrual cycles later, ovarian stimulation was performed for IVF using a time-release gonadotrophin-releasing hormone agonist (GnRHa) and human menopausal gonadotrophin (HMG). For the interpretation of the EFORT results, we considered the post-FSH plasma oestradiol increment (delta E2) and the baseline plasma FSH values (bFSH). The results of these two parameters were compared with the subsequent quality of the ovarian response to stimulation for IVF and the pregnancy outcome. Our results indicated a statistically significant improvement of the predictive value of the bFSH on the ovarian stimulation outcome when the EFORT parameters (bFSH and delta E2) were analysed synergistically.(ABSTRACT TRUNCATED AT 250 WORDS)