SUMMARYReports in the literature indicate that corn at the time of harvest typically is infected (55–92% of the kernels) with a variety of fungi. This study was initiated to determine the time, kind, and progressions of natural fungal infection of corn in the field. During the 1974 growing season, a central Illinois cornfield was sampled weekly (15 wk) from the emergence of silks until harvest. Weather data were recorded. At each sampling, 10 ears were hand picked and brought into the laboratory, where silks, and kernels from tip, middle, and butt of each ear were aseptically removed and plated on yeast extract agar containing tetracycline. After incubation at 28 C for 4–7 da, the fungi growing from the silks and kernels were identified. Fusaria were identified the third week and had a peak occurrence in the eighth week. Yeasts followed the same trend. Overall, Fusaria were by far the most abundant molds infecting the corn kernels.Acremonium strictumwas identified the sixth week, whereasNigrosporasp. was not observed until the eighth week. Both progressively increased to harvest. Species ofAlternariaandPenicilliumwere sporadic and found at low levels. NoAspergillusspecies were encountered. Generally, maturing corn was relatively free of fungal contamination until the late dent stage.