Mycotoxins are naturally occurring toxic chemical compounds produced by fungi infesting agricultural crops both during their growth and storage. Such secondary metabolites, when ingested, can produce toxic syndromes in humans. As it has been suggested that mycotoxins might be involved in the development of Kashin-Beck disease (KBD), we undertook a survey of barley grains of KBD-affected families and non-affected families in that country. We found, by thin layer chromatography, a hitherto unknown metabolite of Alternaria sp. This was especially common on the barley grains of KBD-affected families.