The aim of this study was to see whether the pathophysiology of polycystic ovary syndrome could be altered by suppressing the abnormal cycle of events associated with abnormal gonadotrophins and androgens. Fifteen women with polycystic ovary syndrome were treated with the GnRH agonist Nafarelin at a dosage of 200 micrograms twice daily intranasally for a period of 3 or 6 months. Eight of these women also had a dexamethasone suppression test 0.5 mg four times daily for 48 h before and after treatment with Nafarelin, in order to differentiate between an adrenal and ovarian source for the excess androgens. Gonadotrophins and androgens were well suppressed, LH to a mean of 1.5 IU/l, testosterone to 1.1 nmol/l and androstenedione to 6.4 nmol/l. Three months after discontinuing Nafarelin, all these hormones had returned to pretreatment levels. The ultrasound appearance of the ovaries showed no consistent reduction in ovarian volume or the disappearance of ovarian follicles. Hirsutism showed slight improvement in four out of seven patients. After treatment one patient out of the eight complaining of infertility, conceived spontaneously and one patient ovulated on a reduced dosage of clomiphene. There was no change in the menstrual pattern of the others. Despite the achievement of good hormonal suppression, there was no change in the condition after therapy was discontinued suggesting that whatever the cause of the condition it remains a permanent situation.