Sixteen patients with polycystic ovarian syndrome (PCO) were treated by in-vitro fertilization (26 treatment cycles). The results were compared with 37 normo-ovulatory women with tubal disease (37 treatment cycles). The oestradiol and progesterone levels were higher during the follicular phase in the PCO patients, but were statistically significantly higher only on the day after human chorionic gonadotrophin administration. Although more oocytes were recovered per cycle from the PCO group (19.3 +/- 6.1) than from the control group (5.4 +/- 2.9) with P less than 0.004, the mean numbers of embryos per cycle were similar in both groups (3.7 +/- 2.4 versus 3.6 +/- 2.2, respectively). The pregnancy rate was also comparable in both groups (30.7 versus 29.7%, respectively). The fact that more oocytes are recovered from PCO patients, balances their lower fertilization and cleavage rates. We conclude, therefore, that IVF treatment may be a viable solution for PCO patients resistant to an in-vivo protocol treatment regimes.