Until now at least 25 genetically modified plants were approved for cultivation and commercialization in the U.S.A., Canada, and in the European Community. Consequently methods for the detection of recombinant genes in food derived from transgenic organisms have been developed. A first standardized method based on the Polymerase-Chain-Reaction (PCR) technique to detect recombinant potatoes is still available in Germany. With PCR there is a possibility to amplify specifically very little amounts of DNA using primers corresponding to the gene of interest. Detection of other transgenic plants can be done in most cases with some modifications of this method. Two prerequisites to establish PCR assays are necessary: knowledge of DNA sequence of the recombinant gene, presence of amplifiable DNA in the sample. The present paper describes methods for the detection of transgenic plants and maize and related food products.