The influence of location, year and cultivar on occurrence, level of infestationand Fusarium species spectrum in winter wheat seeds were evaluated. The wheat seeds from different cultivarsand localities of the Slovak Republic were used for Fusarium species evaluation during years 1999, 2000, 2002 and 2003. The significant influence of the locality on total Fusarium kernel infestation was confirmed. The total sample infestation was significantly higher in the colder and moister localities, lower infestation was in warmer and dryer ones. Cultivar Astella was significantly the most susceptible. The widest Fusarium species spectrum was recorded in the locations with a high level of total kernel infestation. In localities with lower infestation, the species spectrum was less numerous. F. poae was the dominant species in alllocations. The species F. culmorum, F. avenaceum and Microdochium nivale were subdominant and relatively frequent in the locations with higher altitude. The frequency and density of other isolated species (F.graminearum, F. sporotrichioides, F. tricinctum, F. semitectum, F. acuminatum, F. heterosporum, F. sambucinum,F. solani, F. compactum and F. oxysporum) was trivial in all localities. The kernel infestation and Fusarium population structure in wheat grains mostly depends on microclimatic condition of the locality. Rising of rainfall rate and altitude led to an increase in the species spectrum. The wide Fusarium species spectrumis connected with the high frequency of coincident species. The species with low and medium frequency achieved low or trivial density in population structure.