Polycystic ovarian syndrome (PCOS) patients have a characteristic of high leuteinizing hormone (LH) to follicle -stimulating hormone (FSH) ratio. Usually, human menopausal gonadotropin (hMG) is used to induce ovulation in clomiphene citrate-resistant PCOS patients. However, HMG contains two components, namely, LH and FSH, with 50%, respectively. Therefore, FSH is theoretically recommended to stimulate follicular maturation. From the pituitary, LH is secreted by pulsatile pattern. So, we have been using intermittent subcutaneous injection of pure FSH for ovulation induction in 10 PCOS patients from March, 1990 to August, 1992. We obtained good results by intermittent subcutaneous injection of pure FSH. Ovulation is 100% per patient, and 88.2% per cycle. Pregnancy rate is 80% per patient, and 23.5% per cycle. Ovarian hyperstimulation syndrome (OHSS) is 50% per patient, 41.2% per all cycles, and 46.7% per all ovulated cycles. In comparison with HMG, pregnancy rate per cycle is relatively low. But, ovulation rate and pregnacy rate per person is higher than HMG. Because of the strict check of ovaries by the vaginal ultrasonography, OHSS rate is relatively high.