Sixteen patients with polycystic ovarian syndrome (PCO) were treated by in-vitro fertilization (IVF), 11 suffered from definitive tubal infertility and five had previously undergone multiple unsuccessful attempts at ovulation induction after conventional therapy. They were randomly allocated into two groups: A1 (six patients) treated with 'pure FSH' and A2 (10 patients) whose ovarian stimulation was performed by a combination of LHRH agonist and pure FSH. More oocytes were recovered in group A1 (7.5 +/- 2.2) and group A2 (10.3 +/- 5.8) than in a control group (B) but this difference was not significant. There was no difference between groups A and B in the number of immature oocytes, the oocyte fertilization rate (60%) and the number of embryos replaced per patient (2.8). Four pregnancies were achieved in the six patients in group A1, 5/9 in group A2 and 3/6 in group B. One severe hyperstimulation was recorded in group A1 but this patient developed a pregnancy which was normal at term. This small study suggests that IVF may be a solution to the treatment of PCO resistant to clomiphene citrate and HMG treatment and that the combination of pure FSH with an analogue of LHRH (in a short protocol of 15 days) does not seem to have an advantage over FSH stimulation alone and does not reduce the frequency of hyperstimulation.