Fusarium moniliforme Sheldon is a common fungal contaminant of corn and produces a variety of mycotoxins. Among these are the recently discovered fumonisins, which are now known to cause certain animal diseases, namely leukoencephalomalacia in horses and pulmonary edema in swine. There is a significant association between their presence in corn and human esophageal cancer in southern Africa. Fumonisin B1 causes liver cancer in rats. Five other fumonisins--B2, B3, B4, A1 and A2, have been isolated; the last two are N-acetates of fumonisins B1 and B2 and do not appear to be toxic. Several other Fusarium species are now known to produce fumonisins. Procedures for detection and determination of fumonisins include thin layer chromatography, liquid chromatography (with fluorescence derivatization), post-hydrolysis gas chromatography, immunochemical assay, and mass spectrometry. In addition to their natural occurrence in corn-based animal feeds and in home-grown African corn used for food, fumonisins are frequently found in commercial corn-based foods. Fumonisins are moderately heat-stable. No effective detoxification process has yet been developed for use with fumonisin-contaminated feeds.