Four experiments using T-2 toxin and nivalenol at different dosage, which represented the 25% and 40% of the LD50 (experiment A: 1.04 mg of T-2 toxin per kilogram of body weight, experiment B: 2.34 mg of T-2 toxin/kg b.w., experiment C: 1.04 mg of T-2 toxin/kg b. w. and 2.34 mg of T-2 toxin/kg b.w.; experiment D: 0.82 mg of nivalenol/kg b.w. and 1.845 mg of nivalenol/kg b.w.) were conducted on 400 mice. Both toxins were administered to mice of different ages (experiments A and B were adults, experiment C and D were young) by intraperitoneal single injection, and the clinical signs, hematological variables and histoanatomo pathological changes were studied. All animals survived. No changes anatomo-histopathological nor significative differences in weight gain were observed. Different behaviors were found for nivalenol and T-2 toxin. The most significant change was the increase in the level of monocytes in old animals, so this could be a biological indicator for T-2 toxin subclinical intoxication.