Twelve oligomenorrhic women with polycystic ovary syndrome (PCO) in whom clomiphene (250 mg daily for 5 days) and 10,000 IU human chorionic gonadotropin had failed to induce ovulation were treated with clomiphene and dexamethasone. Eight of the 12 women underwent complete hormonal assessment during treatment. Six of the 12 ovulated and 1 conceived. Serum total and unbound estradiol and testosterone (T), serum dehydroepiandrosterone sulfate (DHEA-S), sex hormone binding-globulin binding capacity (SHBG-BC), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) were measured during clomiphene and dexamethasone therapy. SHBG-BC increased in response to clomiphene whether or not ovulation occurred. After treatment with clomiphene and dexamethasone there was a significant decrease in serum T, unbound T, and DHEA-S 2 weeks after dexamethasone administration, but there were no change in LH, FSH, or PRL. In patients who ovulated after clomiphene and dexamethasone, T and unbound T increased again after clomiphene was begun despite the continuation of dexamethasone. The women who ovulated after clomiphene and dexamethasone treatment had significantly higher pretreatment levels of DHEA-S than those who did not ovulate. Clomiphene and dexamethasone treatment may be beneficial to women who have elevated levels of DHEAS and who fail to ovulate with maximum doses of clomiphene.