Abstract The effect of T-2 toxin on cell-mediated resistance to bacterial infection was evaluated in mice exposed to Listeria monocytogenes . Mice were inoculated with 4.0 × 10 5 (LD 50) or 4.0 × 10 4 (nonlethal) L. monocytogenes on day 0 and treated orally on days 0, 1, 2, and 3 with 2.0, 1.0, or 0 mg/kg T-2 toxin. Toxin induced suppression of resistance was indicated by the rapid growth of Listeria in the spleen and by significant (P < 0.005) increases in mortality due to listeriosis. Necrosis and depletion of lymphoid tissue, lymphopenia, and a marked decrease in the influx of lymphocytes and macrophages into Listeria elicited peritoneal exudates and at sites of infection in the liver and spleen occured in the toxin treated mice. The immunotoxic effect of T-2 toxin on cell-mediated resistance to listeriosis was dosage dependent and attributed to toxin induced lymphoid depletion and the failure of surviving lymphocytes and mononuclear cells to clear the host of infection.