The aim of this study was to assess the possibility of genetically modified DNA transfer from feed containing RR soybean or/and MON810 maize to animal tissues, gut bacterial flora, food of animal origin, and the fate of GM DNA in the animal digestive tract. The experiment was carried out on broilers, laying hens, pigs and calves. All animals were divided into four groups: I--control group (non-modified feed), II--GM soybean group (non-modified maize, RR soybean), III--GM maize group (MON810 maize, non-modified soybean), and IV--GM maize and soybean group (MON810 maize, RR soybean). Samples of blood, organs, tissues, digesta from the gastrointestinal tract, and eggs were analysed for the presence of plant species specific genes, and transgenic sequences of CaMV 35S promoter and NOS terminator. PCR amplifications of these GM sequences were conducted to investigate the GM DNA transfer from feed to animal tissues and bacterial gut flora. In none of the analysed samples of blood, organs, tissues, eggs, excreta and bacterial DNA were plant reference genes or GM DNA found. A GM crop diet did not affect bacterial gut flora as regards diversity of bacteria species, quantity of particular bacteria species in the animal gut, or incorporation of transgenic DNA to the bacteria genome. It can be concluded that MON810 maize and RR soybean used for animal feeding are substantially equivalent to their conventional counterparts. Genetically modified DNA from MON810 maize and RR soybean is digested in the same way as plant DNA, with no probability of its transfer to animal tissues or gut bacterial flora.