Fusarium fungal contaminants and related mycotoxins were investigated in eight maize feed samples submitted to the Iowa State University Veterinary Diagnostic Laboratory. Fusarium moniliforme, F. proliferatum, and F. subglutinans were isolated from seven, eight, and five samples, respectively. These strains belonged to mating populations A, D, and E of the teleomorph Gibberella fujikuroi. Fusaproliferin was detected at concentrations of 0.1 to 30 microg/g in four samples, and beauvericin was detected (0.1 to 3.0 microg/g) in five samples. Fumonisins were detected in all eight samples (1.1 to 14 microg/g). Ten of 11 strains of F. proliferatum and all 12 strains of F. subglutinans isolated from the samples produced fusaproliferin in culture on whole maize kernels (4 to 350 and 100 to 1,000 microg/g, respectively). Nine F. proliferatum strains also produced beauvericin in culture (85 to 350 microg/g), but none of the F. subglutinans strains produced beauvericin. Fumonisin B1 was produced by all nine F. moniliforme strains (50 to 2,000 microg/g) and by 10 of the F. proliferatum strains (1,000 to 2,000 microg/g). This is the first report of the natural occurrence of fusaproliferin outside Italy and of the natural occurrence of beauvericin in North America.