Fusarium spp invades grain commodities in the field and during storage in Uruguay and produces Deoxynivalenol as the main toxin. The Department of Natural Toxins of Technological Laboratory of Uruguay, as partner in the Project titled The Development of a Food Quality Management System for the Control of Mycotoxins in Cereal Production and Proccesing Chains in Latin America South Cone Countries, INCO Project ICA4-CT-2002-10043 participates in two workpackages (WP). WP1 related to the development and standarisation of effective analytical tools for mycotoxin determination in cereal and by- products and WP4 related to hazard analysis on mycotoxins. Once DON results were obtained, the objective of this work was to evaluate a possible relationship between the level of deoxynivalenol contamination in wheat and the fungi infection. To reach the objective nine samples corresponding to four different levels of DON contamination were selected as representative of the 87 samples. One sample of 1379 ppb (Group A), four samples of 2536 ppb average (Group B), one sample of 7349 ppb (Group C) and three samples of 20076 ppb average (Group D) were used for the study. The water activity (aw) was measured previous DON content analysis and fungi contamination determination. The values recorded were lower than 0,7. The grains, before and after treatment with sodium hipocloride solution 5%, were placed in duplicate Petri dishes containing yeast glucose cloramphenicol agar (YGCA), twenty grains without treatment and fourty grains treated per dish. The colonies grown were isolated in potato dextrose agar (PDA) and malt extract agar (MEA) tubes. Cultures on Czapek Agar were made. Petri dishes and tubes were incubated at 25 ± 1 °C, 4 to 7 days. Cultures on Cazapek Agar were observed under microscope every 24 hours. After sodium hipocloride treatment Fusarium, Penicillium and Alternaria spp were found. The results obtained showed that Fusarium spp colonies were isolated from five samples: one of group A corresponding to three isolates, two of group B corresponding to two and three isolates and two of group D corresponding to five and eight isolates. Penicillium was recovered from three samples