We aimed to compare the effects of two different gonadotropins on steroid production in patients with polycystic ovary syndrome (PCOS). The study group comprised 20 infertile patients diagnosed with PCOS who were accepted into in vitro fertilization-embryo transfer and gamete intra-Fallopian transfer programs. Ten patients were consecutively allocated to a purified urinary follicle stimulating hormone (FSH) administration group while the other tert received human menopausal gonadotropin (hMG). All patients were pretreated with a gonadotropin releasing hormone-agonist. The patients were followed by daily vaginal ultrasonography until at least two follicles reached a diameter of 17 mm or an estradiol value of at least 100 pg/ml per follicle. To induce ovulation, human chorionic gonadotropin was given. On the 3rd day of menstruation, serum estradiol, luteinizing hormone (LH), FSH, total testosterone, androstenedione, dehydroepiandrosterone sulfate (DHEAS), insulin-like growth factor-I and insulin were measured. These same parameters were measured again on the day of follicle aspiration in both serum and follicular fluid. In both groups, the serum levels of estradiol and androstenedione were raised significantly, and on aspiration day the serum level of DHEAS was significantly raised in the FSH group but not in the hMG group. Our findings suggest that in PCOS patients exogenous hMG induces a different steroid synthesis pattern compared to pure FSH, hypothetically by reduction of the Delta-5 steroid synthesis pathway in the adrenals and/or in the ovary.