Objective To observe the effects of Dexamethasone (Dex), a synthetic glucocorticoid, on glucocorticoid receptor expression in the human ovarian carcinoma cell line 3AO. The molecular mechanism of glucocorticoid (GC) on 3AO cells was also studied.Methods The expression and regulation of the glucocorticoid receptor in 3AO cells was studied by utilizing radioligand binding assay and quantitative RT-PCR. Results High affinity and low capacity GR existed in 3AO cells, in addition, GR binding activity was down-regulated by Dex in a time-dependent manner, to a level about 28.34% of control following 24 hours treatment, with a concomitant decrease in GR mRNA. The induction of alkaline phosphatase (AKP) activity by Dex was reversed by RU486, a potent glucocorticoid antagonist.Conclusion In 3AO cells, functional GR which can be down-regulated by Dex at the protein and mRNA level, exists suggesting that the regulating effects of Dex on GR occur at least partially at the GR mRNA level, and that the cellular effects of Dex on 3AO cells might be mediated by GR.