Forty-three strains of Fusarium moniliforme isolated from infected maize and sorghum plants in Italy were assayed for their ability to produce fertile crosses with "A" and "F" mating population tester strains, in relation to their ability to produce fumonisins on maize substrate. Most of the strains isolated from maize (ear and stalk rot and maize-based feed), producing fumonisin B1 (FB1) and B2 (FB2) (up to 4,100 and 855 mg/kg, respectively), belonged to the "A" mating population. All of the strains isolated from sorghum belonged to the "F" mating population and produced little or no FB1 and FB2. This is the first report of the occurrence of mating population "F" in Europe. Our data on strains from Italy are consistent with previous studies from the United States that found significant differences in sexual fertility and fumonisin production between strains from maize and sorghum.