The subacute toxic effects of dietary T-2 toxin were compared in young male Wistar rats, young male Swiss mice and juvenile Swiss mice. Purified T-2 toxin was fed in the diet at levels of 10 or 20 ppm for 2 or 4 weeks. Dose-related depressions in food consumption and weight gain consistently occurred in all animals fed T-2 toxin. Hyperkeratosis of the squamous gastric mucosa, atrophy of the thymus and thymus-dependent lymphoid tissues, and lymphopenia occurred in all animals exposed to T-2 toxin. These effects were most severe in juvenile mice, and least severe in rats. In addition, juvenile mice fed the 20-ppm level developed erythroid hypoplasia and became severely anemic by 4 weeks. These results demonstrate that dietary T-2 toxin at levels up to 20 ppm cause similar effects attributable to food refusal and alimentary irritation in both species. However, mice and rats were relatively resistant to hematopoietic suppression. Only the juvenile mice fed 20 ppm developed this potentially lethal toxic effect.