The study was designed to examine whether dynamic measurements of inhibin B and oestradiol following single administration of buserelin acetate were correlated with the ovarian response to stimulation in IVF. A total of 37 patients undergoing IVF treatment was studied when the long protocol was started in the early follicular phase. Blood samples were taken twice: on day 2 of the menstrual cycle, before the first s.c. administration of buserelin acetate 0.5 mg and on day 3, 24 h later. Inhibin B and oestradiol concentrations were compared with the ovarian response to stimulation. The ovarian response was defined in two ways: 'number of oocytes/total recombinant (r) follicle stimulating hormone (FSH) dose'; and 'square-root (number of follicles/total rFSH dose)'. The following measurements were highly correlated with the ovarian response to stimulation: increase in oestradiol (day 3-day 2 oestradiol concentration) [correlation coefficient (r) = 0.68, P: < 0.0001] and sum of inhibin B (day 2 + day 3 inhibin B concentrations) (r = 0.6, P: < 0.0001). Age and basal concentrations of FSH and inhibin B were inferior to the above measurements in terms of correlation with the ovarian response. In conclusion, dynamic measurements of inhibin B and oestradiol following single administration of buserelin acetate were highly correlated with the ovarian response to stimulation for IVF treatment.