This report describes the preparation and certification of dry mixed maize powder CRMs (IRMM-413-0) with different mass fractions of genetically modified MON 810 maize powder (Certified reference materials IRMM-413-0, IRMM-413-1, IRMM-413-2, IRMM-413-3, IRMM-413-4 and IRMM-413-5). The CRMs were produced by the Institute for Reference Materials and Measurements (IRMM) in 2000 in collaboration with the Institute for Health and Consumer Protection (IHCP, Ispra, IT), both Joint Research Centres of the European Commission. The CRMs are intended for the validation and calibration of methods for the detection of genetically modified food. The MON 810 concentration of IRMM-413 was verified with the help of DNA based and protein based detection methods. The CRMs are available in the form of glass bottles containing 1 g of maize powder packed under argon atmosphere. Seeds of non-modified maize (variety DK 512 delivered by R.a.g.t. Semences, Rodez, France) and MON 810 (cultivar DK 513 delivered by R.a.g.t. Semences, Rodez, France) were rinsed with demineralised water, additionally drained and dried at 30°C in order to minimise dust contamination from other crops. An average particle size in the maize powder of 35 µm was reached by cryo-grinding. The materials were prepared by quantitative Turbula and dry-mixing of non-modified maize powder and 100 % MON 810 GMO maize powder. After bottling the pre-filled bottles were submitted to a supplemental primary vacuum drying for around 2 h and closed after filling with pure argon. It is recommended to use samplings not smaller than 100 mg. Bottles should be stored dry and cool (+4 °C) and kept in the dark.