OBJECTIVE To investigate the role of follicle stimulating hormone receptor (FSHR) expression on granulosa cells in ovarian response of women undergoing gonadotropin stimulation. METHODS A total of 60 women were recruited and divided into poor, moderate and high responders according to the number of follicles. FSHR expression was detemined by Western blot on granulosa cells obtained by follicular aspiration. The peak levels of serum estradiol (E(2)) were measured by immunofluorescent assay. RESULTS (1) The expression of FSHR was significantly different among the 3 groups, being 0.19 +/- 0.07, 0.34 +/- 0.16, and 0.45 +/- 0.18 for poor, moderate and high responders, respectively (P < 0.001). Poor responders had the lowest peak levels of serum E(2) and the least number of follicles. (2) The FSHR was positively correlated with peak level of E(2) in serum and the number of follicles (P < 0.01 for both). CONCLUSION Ovarian response to gonadotropin stimulation depends on the different levels of FSHR expression on granulosa cells.