We analyzed 44 moldy corn samples for the B and C series of fumonisins by high-performance liquid chromatography. Of the 44 samples, 32 (73%) were contaminated with both the B and C series of fumonisins and 6 were contaminated with only the B series of fumonisins. The incidence of fumonisin C1 in moldy corn was 71%; the incidence was 11% for fumonisin C3 and 43% for fumonisin C4. Their mean levels ranged from 500 to 1,900 ng/g. This is the first report on the natural occurrence of the C series of fumonisins and fumonisin B4 in moldy corn.