As glucocorticoid resistance (GCR) and the concomitant burden pose a worldwide problem, there is an urgent need for a more effective glucocorticoid therapy, for which insights into the molecular mechanisms of GCR are essential. In this study, we addressed the hypothesis that TNFα, a strong pro-inflammatory mediator in numerous inflammatory diseases, compromises the protective function of the glucocorticoid receptor (GR) against TNFα-induced lethal inflammation. Indeed, protection of mice by dexamethasone against TNFα lethality was completely abolished when it was administered after TNFα stimulation, indicating compromised GR function upon TNFα challenge. TNFα-induced GCR was further demonstrated by impaired GR-dependent gene expression in the liver. Furthermore, TNFα down-regulates the levels of both GR mRNA and protein. However, this down-regulation seems to occur independently of GC production, as TNFα also resulted in down-regulation of GR levels in adrenalectomized mice. These findings suggest that the decreased amount of GR determines the GR response and outcome of TNFα-induced shock, as supported by our studies with GR heterozygous mice. We propose that by inducing GCR, TNFα inhibits a major brake on inflammation and thereby amplifies the pro-inflammatory response. Our findings might prove helpful in understanding GCR in inflammatory diseases in which TNFα is intimately involved.