White rats given intragastrically 3alpha-hydroxy-4beta,15-diacetoxy-8alpha-(3-methylbutyryloxy)-12,13-epoxy-tricholthec-9-en (T-2 toxin), a trichothecene metabolite of several Fusarium species, developed various acute and chronic, topical and systemic lesions. The rats that survived 12 to 27.5 months after the first of three to eight doses of T-2 toxin (0.2 to 4 mg/kg body weight) alone or in conjunction with nicotinamide given i.p. (200 to 250 mg/kg body weight) developed cardiovascular lesions of various degrees of severity and/or tumors, benign and malignant, of the digestive tract and of the brain. T-2 toxin is known occasionally to contaminate cereals and other agricultural products, harvested or stored under damp and cold conditions. T-2 toxin was responsible for an often fatal disease in humans, known in the U.S.S.R. as "alimentary toxic aleukia," and also for outbreaks of hemorrhagic mycotoxicoses in livestock in various countries. T-2 toxin and other Fusarium mycotoxins may be involved in the etiology of cardiovascular lesions and of certain tumors considered as "spontaneous" in animals and humans.