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Investigou-se a incidência de desoxinivalenol (DON), nivalenol (NIN), diacetoxiscirpenol (DAS) e toxinas T-2 (T2) e HT-2 (HT2) em 80 amostras de milho do estado de São Paulo/ Brasil, coletadas nos silos de duas cooperativas deste estado. As amostras foram extraídas com água/ acetonitrila e purificadas com colunas Mycosep. Após derivatização com anidrido trifluoroacético as amostras foram analisadas por cromatografia gasosa-espectrometria de massas. Os limites de detecção ficaram entre 10 ng g -1 e 40 ng g -1. NIV foi encontrada em 5 amostras e DON e NIV ocorreram simultaneamente numa das amostras. DAS, T2 e HT2 não foram detectadas. Este é o primeiro relato que mostra a prevalência de NIV sobre DON em milho do Brasil.The incidence of deoxynivalenol (DON), nivalenol (NIV), diacetoxyscirpenol (DAS), and toxins T-2 (T2) and HT-2 (HT2) in 80 samples of commercial corn harvested in the state of São Paulo, Brazil. They were collected in the silos of the two largest corn farmer's cooperatives of this state. The samples were extracted with water/acetonitrile and cleaned-up with MycoSep columns. After trifluoroacetic anhydride derivatization the samples were submitted to gas chromatography-mass spectrometry. Detection limits ranged from 10 ng g -1 to 40 ng g -1 . NIV was present in 5 samples and DON and NIV occurred simultaneously in one sample. DAS, T2 and HT2 were not detected. This is the first report that shows the prevalence of NIV over DON in corn harvested in Brazil. Keywords: corn, GC-MS, trichothecenes, deoxynivalenol, nivalenol IntroductionTrichothecenes constitute a group of toxic substances produced mainly by Fusarium among several different fungal genera.1 These compounds have in common the presence of the system 12, 13 -epoxy-trichotec-9-en in their structures.2,3 Diacetoxyscirpenol (DAS) and the toxins T2 (T2) and HT2 (HT2), deoxynivalenol (DON) and nivalenol (NIV) are among the trichothecenes with greater natural occurrence in food and feed. [4][5][6] The ingestion of feed contaminated with trichothecenes has been shown to be toxic and to cause feed refusal, emesis, diarrhea, anorexia, hematological and immunological alterations and even death. Similar symptoms have been observed in humans exposed to trichothecenes. 1,2,4,7 Trichothecenes occur in cereals worldwide 6 and contamination in corn is frequently reported. [8][9][10][11][12][13][14][15] There is little information about corn cultivated in Brazil. Prado et al. 16 found DON in about 6% of post-harvested corn samples with levels ranging from 102 to 542 ng g -1 in contaminated samples and 104 ng g -1 T2 in one sample. Oliveira et al. 17reported the presence of DON in 6% of samples of popcorn in levels ranging from 30 to 770 ng g -1 . Several methods are used to determine trichothecenes, such as thin layer chromatography, liquid chromatography, gas chromatography, and immunoassays. 7,18,19 More recently some methods have been developed using the liquid chromatography/tandem mass spectrometry for identification and determination of trichothecenes type...