Maternal glucocorticoid treatment affects estrogen synthesis by decreasing estrogen precursors. Whether glucocorticoid has any effect on the placental conversion of estrogen precursors to estrogen is not known. A study was therefore undertaken to investigate the effect of 100 mg of intravenously administered dehydroepiandrosterone sulfate (DHEAS) on estradiol (E2), estriol (E3), and testosterone (T) serum levels. The test was conducted for 5 hours in 10 women treated with intramuscular dexamethasone and in 8 controls during the last trimester of pregnancy. The initial E2 and E3 serum concentrations were lower in women treated with dexamethasone than in controls, while T serum levels did not display any difference. Following the injection of DHEAS there was a significant increase in E2, with maximal levels reached between 1 and 3 hours after injection in both groups. Maximal levels of E2 were equal for both groups. There was no change in E3 levels after DHEAS administration in the nontreated group, while the increase in the dexamethasone group was significant. A significant rise in T, with maximal levels reached at 1 hour after infusion, was similar in both groups. It is concluded that maternal dexamethasone does not inhibit the conversion of DHEAS either to E2 in the placenta or to E3 and T.