Acute toxic effects of several 12,13-epoxytrichothecenes were investigated in 1-day-old broiler chicks by single oral doses. The 7-day median lethal dose values of purified 8-acetylneosolaniol, diacetoxyscirpenol, T-2 toxin, HT-2 toxin, neosolaniol, deacetyl-HT-2 toxin, and T-2 tetraol were 3.22 +/- 0.26, 3.82 +/- 0.40, 4.97 +/- 0.44, 7.22 +/- 0.39, 24.87 +/- 2.64, 30.18 +/- 7.53 (incomplete value), and 33.79 +/- 5.39 mg/kg of body weight, respectively. Deaths occurred during the 8- to 60-h period after dosing with the tested trichothecenes. Within 4 to 10 h after dosing, inappetence, asthenia, diarrhea, and coma generally developed. Sublethal doses of each toxin decreased feed consumption and weight gain proportionally with the amounts of toxins administered. These results demonstrate that the toxic potency of 12,13-epoxytrichothecenes varies depending on the modification of side chains in the molecule.