The persistence and movement of transgenic DNA in ecosystems is largely unknown. This movement poses a threat of horizontal gene transfer and possible proliferation of genetically modified DNA into the environment. Using quantitative PCR, authors identified the cp4 epsps transgene in soil microarthropods, nematodes, macroarthropods and earthworms living in a field of transgenic corn. The results are the first to demonstrate the persistence of transgenic crop DNA residues within a food web.