Objective To study prospectively the values of basal and dynamic measurement of inhibin B(INHB), estrodiol (E_2)following gonadotrophin therapy in vitro fertilization(IVF)cycles in predicting ovarian response to stimulation in young women. Methods A total of 57 patients younger than 40 years of age undergoing their first cycle of long protocol IVF treatment were studied and serum INHB, E_2 levels were detected on day 3 of the menstrual cycle, before the first administration of gonadotrophin (day 0), on days 1 and 5 after gonadotrophin therapy(day 1, day 5 ). Ovarian response was presented by: number of oocytes/total rFSH dose and square root of (number of follicles/total rFSH dose). According to number of follicles, number of oocytes and presence or absence of ovarian hyperstimulation syndrome(OHSS), we categorized the results into three different groups: poor response, normal response and OHSS. Results (1) Hormone levels on days 1,5 of rFSH stimulation: There were positive correlation between INHB (r_S:0.69-0.73), E_2 (r_S:0.60-0.73) and ovarian response (P=0.000). (2) INHB, and E_2 levels on day 5 of rFSH stimulation were significantly different between poor response, normal response and OHSS groups(P