Two studies were conducted with weanling male rodents in an attempt to ascertain more precisely the toxic effects of deoxynivalenol (DON). In a feeding study of approximately 18-wk duration, groups of 90 Swiss-Webster derived mice and 50 Sprague-Dawley rats were fed a commercial chow (118 ppb DON), and groups of 80 mice and 50 rats were fed either an 'uncontaminated' diet (53 ppb DON) or a contaminated diet (6250 ppb DON), both based on wheat. A 5-wk gavage study was also performed, in which 24 litters of 5 Swiss-Webster-derived mice were divided among the following groups: an untreated control group, a solvent control group, and three treated groups receiving 0.75, 2.5 or 7.5 mg DON/kg body weight. While there were interim kills in the feeding study, most of the animals given 7.5 or 2.5 mg/kg in the gavage study died during the test period. Effects on body weight and haematological parameters in both studies indicate that DON elicited some degree of toxicity at all levels tested. The histopathological findings from the gavage study suggest that DON had effects on the immune system as well as being a gastro-intestinal irritant.