To evaluate whether the addition of finasteride (a 5〈-reductase inhibitor) to conventional protocol of ovarian stimulation with gonadotropin can improve ovarian follicular growth in polycystic ovary syndrome (PCOS) women who did not respond to previous stimulation with gonadotropin alone.Double-blind randomized study.Outpatient in an academic research environment.Thirty-six PCOS patients in whom the previous multifollicular stimulation protocols with gonadotropin failed.The patients were randomly assigned to two treatment groups: group 1 underwent ovarian stimulation with recombinant FSH (rFSH) plus finasteride, and group 2 received rFSH alone. When the dominant follicle reached a mean diameter of 18 mm, hCG was administered and finasteride withdrawn.Ovulation rate in women with PCOS.Follicular growth and ovulation occurred in eight patients in group 1, whereas no cases were detected in group 2.This study confirms that hyperandrogenism interferes with follicular growth and suggests that administration of finasteride during ovarian stimulation with rFSH improves ovulation rate in selected hyperandrogenic anovulatory women.