In 2003-2005 micromycetes were isolated and identified from wheat, barley,rye, buckwheat grain brought into mills or from processing enterprises. Contamination of the producedflour with micromycete propagules (cfu g(-1)), changes in micromycete diversity and abundance in thecourse of flour storage, preparation and baking of bread, production of groats or other food productsand fodder were determined. Most attention was given to widely distributed micromycetes, known producersof toxins: Alternaria alternata, Aspergillus candidus, A. clavatus, A. flavus, A. fumigatus, A. niger,A. oryzae, A. (=Eurotium) repens, Fusarium culmorum, F. equiseti, F. graminearum, F. moniliforme, F.oxysporum, F. poae, F. sporotrichioides, Penicillium brevicompactum, P. chrysogenum, P. cyclopium, P.daleae, P. expansum, P. funiculosum, P. roqueforti, P. urticae, P. verruculosum, P. viridicatum, Phomaexiqua, Rhizomucor pusillus, Rhizopus stolonifer, Trichothecium roseum. Abilities of these micromycetesto produce secondary toxic metabolites were determined as well as possible hazard caused to people consumingthe contaminated products.