The purpose of the present study was to determine whether adrenal androgen suppression with dexamethasone (DEX) during ovulation induction improves the outcome of in-vitro fertilization (IVF) cycles. A total of 25 patients with serum dehydroepiandrosterone sulphate (DHEAS) concentrations > 2.5 micrograms/ml were randomized to receive either 0.5 mg DEX daily or placebo during ovulation induction with leuprolide acetate down-regulation plus human menopausal gonadotrophins (HMG). Nine patients undergoing a subsequent IVF cycle were crossed over to the other treatment group. Ovarian responsiveness and IVF outcome variables analysed included number of follicles > 12 mm in diameter, serum oestradiol concentrations on the day of human chorionic gonadotrophin (HCG) administration, number of ampoules of HMG administered, number of oocytes retrieved, percentage of oocytes fertilized, number of embryos transferred, implantation rate and numbers of clinical pregnancies and live birth pregnancies. The 31 randomized IVF cycles revealed a trend towards a higher implantation rate for the placebo-treated group compared to the DEX-treated group (24 versus 10%; P = 0.07). The remainder of the IVF cycle variables revealed no statistically significant differences. In conclusion, the suppression of adrenal androgens with DEX in women with DHEAS concentrations > 2.5 micrograms/ml appears to have no beneficial effects on ovarian responsiveness or clinical or live birth pregnancy rates.