Kernels of three maize varieties namely: Fraz 23, Fraz 34 and Bendel White planted in Eastern Nigeria in 1982 and 1983 planting seasons were screened for seed‐borne fungi. The effects of Thioral (a.i. 25% heptachlor and 25% TMTD), a biocidal seed‐dressing chemical, on seed‐borne fungi and on kernel viability were also investigated. Results showed that kernels of the three maize varieties screened harbouredFusarium moniliforme. Fusarium nivale, Fusarium semitectum, Aspergillius flavus. Penicillium oxalicum, Curvularia pallescens, Rhizopusspp. andSac‐charomycesspp. at appreciable high percentages.Fusariumspecies dominated the other fungi. These fungi caused appreciable reduction in the percentage kernels germinating. In Thioral‐treated kernels,F. moniliforme, F. Nivale, F. semitectum. P. oxalicum, C. pallescens, Rhizopus spp.andSaccharoymcesspp. were completely eliminated or reduced. The percentage kernel germination increased significantly(P= 0.001) and no phytotoxic effects were observed on the kernels’ seedlings treated with Thioral. The mean percentage incidence ofA. flavusisolated in Thioral‐treated kernels increased when compared with the untreated kernels in all the three maize varieties.