Mycotoxins have for long been associated with disease and death in animals, but because of the great variety of fungi present in animal feedstuffs and the detailed investigations needed to establish a causal relationship between mycotoxin and a clinical disease, few disease syndromes have been identified.In this paper, it is proposed to consider three confirmed clinical diseases caused by mycotoxins, to review briefly their history and identification and to consider their biological effects in ruminants.