Inst. of Microbiology & Biochemistry, National Taiwan Univ., Taipei 106 TaiwanProduction of genetically modified (GM) crops is currently concentrated in just afew countries while more countries are experimenting new traits. For 2003, 99% ofGM crops are produced in four countries, i. e. US 63%, Argentina 21%, Canada 6%,Brazil and China 4%. Crop-wise, GM soybean made up 61% of global area and GMcorn accounts for 23% followed by GM cotton (11%) and GM canola (5%).Compared with the global planting area, GM soybean and cotton accounted for 55%and 21%, respectively. Two major GMO traits in 2003 were herbicide tolerant crops,accounted for 73% of all GM crops, while Bt crops accounted for 18%.Legislation enacted worldwide to regulate the presence of genetically modifiedorganisms (GMOs) in crops, foods and ingredients, necessitated the development ofreliable and sensitive methods for GMO detection. In this article, protein- andDNA-based methods employing western blots, enzyme-linked immunosorbant assay,lateral flow strips, Southern blots, qualitative-, quantitative-, real-time- and limitingdilution-PCR methods, are discussed. Where information on modified gene sequencesis not available, new approaches, such as near-infrared spectrometry, might tackle theproblem of detection of non-approved genetically modified (GM) foods. Theefficiency of screening, identification and confirmation strategies should be examinedwith respect to false-positive rates, disappearance of marker genes, increased use ofspecific regulator sequences and the increasing number of GM foods.In Taiwan all foods containing more that 5% GMO must be labeled, and theDNA-based methods are the most popular ones. Typical detection methods are thefollowing: Western blots, Enzyme-Linked Immuno-Sorbant Assay (ELISA), Lateralflow strips, Southern blots, real-time- and limiting dilution-PCR methods being thislast one the most commonly used. Significant efforts are underway to identify properdetection methodology for GMO content in fermented food from soybean, i.e. misoand sufu. Standard PCR and nested PCR cannot give positive results to the detectionof the transgenic components in miso. Standard PCR system failed to detect RoundupReadyTM soybean (RRS) in sufu, while nested PCR can detect RRS in sufu.