Regulations for the use and labeling of genetically modified (GM) products and derived ingredients were implemented in Brazil in 2003.  In 2008, GM maize line MON810 was approved for commercialization in Brazil; nevertheless, maize Bt11, Bt176 and MON810 were found in Brazilian market products sold in 2000 and 2001.  Nested polymerase chain reaction (PCR) method was employed to monitor the presence of MON810 in 81 maize-derived products (maize flour, corn meal, maize flour flakes and polenta) that are sold in Brazilian markets from 2005 to 2007, after the implementation of genetically modified organism (GMO) labeling regulation.  The sensitivity of nested PCR for MON810 detection was 0.1%.  CTAB protocol was suitable for the extraction of amplifiable maize DNA from maize flour, corn meal, maize flour flakes, and polenta.  MON810 GM maize line was not detected by specific nested PCR in 81 samples of maize-derived food sold in Brazil from 2005 to 2007.  This paper reports data concerning the detection of GM maize after publishing Brazilian regulations that stipulate directions for using and labeling of foods and ingredients containing GMOs.