The effect of dexamethasone (DEX) (9α-Fluro-16α-methyl prednisolone) on secretion of steroids by human granulosa luteinized cells was studied by culturing cells from mature follicles of women with polycystic ovarian disease and treated for infertility in the in vitro fertilization program. Patients were treated with DEX 0.5 mg/d until the day of human chorionic gonadotropin administration. The cells were cultured for 24 hours in the presence of androstenedione (10-7 M). After incubating for 24 hours, the medium was replaced and the cells were incubated for an additional 24 hours. The medium was then harvested and assayed for estradiol (E2) and progesterone (P). Results were compared with those of a control group who was not treated with DEX. Estradiol production by cells was significantly lower in the study group treated with DEX. Progesterone production was not influenced by DEX. Follicular fluid levels, E2, and androgens did not vary with DEX treatment, whereas cortisol levels markedly decreased and P levels increased with the treatment. These findings suggest that glucocorticosteroids can directly influence granulosa luteinized cell function.