Background: Since their first commercialization, the diversity of taxa and the genetic composition of transgenesequences in genetically modified plants (GMOs) are constantly increasing. To date, the detection of GMOs andderived products is commonly performed by PCR-based methods targeting specific DNA sequences introducedinto the host genome. Information available regarding the GMOs' molecular characterization is dispersed and notappropriately organized. For this reason, GMO testing is very challenging and requires more complex screeningstrategies and decision making schemes, demanding in return the use of efficient bioinformatics tools relying onreliable information.Description: The GMOseek matrix was built as a comprehensive, online open-access tabulated database whichprovides a reliable, comprehensive and user-friendly overview of 328 GMO events and 247 different geneticelements (status: 18/07/2013). The GMOseek matrix is aiming to facilitate GMO detection from plant origin atdifferent phases of the analysis. It assists in selecting the targets for a screening analysis, interpreting the screeningresults, checking the occurrence of a screening element in a group of selected GMOs, identifying gaps in theavailable pool of GMO detection methods, and designing a decision tree. The GMOseek matrix is an independentdatabase with effective functionalities in a format facilitating transferability to other platforms. Data were collectedfrom all available sources and experimentally tested where detection methods and certified reference materials(CRMs) were available.Conclusions: The GMOseek matrix is currently a unique and very valuable tool with reliable information on GMOsfrom plant origin and their present genetic elements that enables further development of appropriate strategies forGMO detection. It is flexible enough to be further updated with new information and integrated in differentapplications and platforms.