Corn collected in the Mazandaran and Isfahan Provinces of Iran was analyzed for fumonisin B(1) (FB(1)), fumonisin B(2) (FB(2)), and fumonisin B(3) (FB(3)). The samples from Mazandaran Province, situated on the Caspian littoral of Iran, were random samples from farmers' corn lots collected in September 1998, whereas those from Isfahan Province, situated further south in the center of Iran, were bought as corn cobs in the local retail market during October 1998. All 11 samples from Mazandaran showed high levels of fumonisin contamination with FB(1) levels between 1.270 and 3.980 microg/g, FB(2) levels between 0.190 and 1.175 microg/g, and FB(3) levels between 0.155 and 0.960 microg/g. Samples from Isfahan showed lower levels of contamination with eight of eight samples having detectable FB(1) (0.010-0.590 microg/g), two of eight samples having detectable FB(2) (0.050-0.075 microg/g), and two of eight samples having detectable FB(3) (0.050-0.075 microg/g). This is the first report of fumonisin contamination of corn from Iran, in which samples from the area of high esophageal cancer on the Caspian littoral have been shown to contain high levels of fumonisins.