Records of the Toxicology Laboratory, Veterinary Services Branch, Ontario Ministry of Agriculture and Food, indicate that 277 of 2,022 specimens of feedstuffs submitted between October 1, 1972 and September 30, 1978 contained one or more mycotoxins. The data indicate that zearalenone is an important mycotoxin in the provincial corn crops and that its incidence fluctuates from year to year. The percentages of specimens containing zearalenone were 16.3 (1972), 4.1 (1973), 5.5 (1974), 22.4 (1975), 9.5 (1976) and 13.0 (1977). Aflatoxins, ochratoxins and T-2 toxin were found in some specimens but their incidence was low.