Glucocorticoid receptor (GR) functions as a suppressor of inflammation by inhibiting the expression of many cytokine genes activated by NF-${kappa}B$. The goal of this study is to investigate the mechanism by which GR repress NF-${kappa}B$ activation in lung epithelial cells. We used A549 and BEAS-2B lung epithelia! cell lines. Using Ig$G{kappa}$-NF-${kappa}B$ luciferase reporter gene construct, we found that dexamethasone significantly suppressed TNF-$alpha$-induced NF-${kappa}B$ activation and the overexpression of GR showed dose-dependent reduction of TNF-$alpha$-induced NF-${kappa}B$ activity in both cell lines. However, DNA binding of NF-${kappa}B$ induced by TNF-$alpha$ in electromobility shift assay was not inhibited by dexamethasone. Super shift assay with anti-p65 antibody demonstrated the existence of p65 in NF-${kappa}B$ complex induced by $alpha$ Western blot showed that $I{kappa}B{alpha}$ degradation induced by TNF-$alpha$ was not affected by dexamethasone and $I{kappa}B{kappa}$ was not induced by dexamethasone, neither. To evaluate p65 specific transactivation, we adopted co-transfection study of Gal4-p65TA1 or TA2 fusion protein expression system together with 5xGal4-luciferase vector. Co-transfection of GR with Gal4-p65TA1 or TA2 repressed luciferase activity profoundly to the level of 10-20% of p65TA1- or TA2-induced transcriptional activity. And this transrepressional effect was abolished by co-transfection of CBP of SRC-1 expression vectors. These results suggest that GR-mediated transrepression of NF-${kappa}B$ in lung epithelial cells is through competing for binding to limiting amounts of transcriptional coactivators, CBP or SRC-1.