This study was intended to assess the effects of oral contraceptives given before treatment in infertile anovulatory patients with polycystic ovary syndrome who receive gonadotropins for controlled ovarian stimulation. Pretreatment with oral contraceptives increased the mono-ovulatory cycles, the duration of stimulation for noncanceled cycles, and the number of vials of gonadotropins used. It also reduced the number of dominant follicles and the peak E(2) levels for dominant follicles. No effect was observed in rates of cycle cancellation, pregnancy, abortion, live birth, multiple pregnancies, and ovarian hyperstimulation syndrome.