Human toxicosis induced by consumption of foodstuffs contaminated with trichothecenes presents one common major symptom: a haematological perturbation manifesting principally as thrombocytopenia and leukopenia. The patients have rapidly progressing coagulation problems, and compromised resistance to infections. Consequently, they are subject to septicaemia and massive haemorrhages. In horses, cattle, poultry, cats, mice and guinea pigs, subacute and subchronic ingestion of trichothecenes causes a decrease of circulating blood cells frequently associated with bone marrow failure. The origins of haematological effects observed in Fusarium toxin intoxications have been elucidated using in vitro tests. Haematopoietic progenitors are the main target of trichothecenes. Deoxynivalenol (DON) is the least myelotoxic and T-2 the most. As circulating blood cells present a less important sensitivity to these toxins, haematological troubles observed in toxicosis are due to myelotoxicity of these toxins.