2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) acute toxicity is characterized in part by a wasting syndrome with depletion of adipose tissue. Tumor necrosis factor (TNF) induces a similar response during chronic infection. The similarities of these toxic effects led to a hypothesis that TNF plays a role in TCDD acute toxicity. To test this hypothesis pharmacologic doses of an antibody specific for murine TNF and the potent anti-inflammatory agent Dexamethasone (DEX) were used to inhibit TCDD toxicity in mice. TNF antibody treatment resulted in a 54% reduction in TCDD-mediated mortality while DEX treatment, a glucocorticoid agonist that inhibits transcription of TNF, reduced mortality by 92%. Cyp 1A1 induction, the most commonly measured TCDD-mediated response, was not blocked by DEX, demonstrating separation of this biochemical effect from acute toxic responses to TCDD. These data suggest that TCDD-mediated changes in the TNF pathway may be an important mechanism for acute TCDD toxicity.