The putative involvement of mycotoxins in human diseases, including cancer, is reviewed with reference to ergotism, citreoviridin toxicosis, alimentary toxic aleukia, stachybotryotoxicosis, Balkan endemic nephropathy and aflatoxicoses. Analytical and sampling problems in determining the occurrence of and exposure to mycotoxins are discussed against the background that over 300 mycotoxins have been identified, produced by some 350 fungal species, and that the potency of some of them demands the quantitation of extremely small quantities of analyte. Mycotoxins associated with food and originating from Alternaria, Aspergillus, Fusaria, Penicillia and Claviceps spp. are reviewed with reference to the toxicological, regulatory and economic issues arising. It is concluded that continued efforts are needed to: identify and quantify human/animal exposure; estimate health risks and make defensible risk-benefit judgements; develop sampling plans based on experimental observation; arrive at agreed regulatory levels based on legitimate sampling plans, analytical capabilities and economic considerations; develop procedures for disposal of contaminated lots; and develop plant varieties resistant to fungal invasion.