Agricultural activities involve the use of oilseed cakes as a source of proteins for livestock. Because the storage of oilseed cakes could induce the development of molds and the production of mycotoxins, a survey was conducted during the 5 months of farm storage. Mycoflora was studied by microscopic examinations, and the presence of Aspergillus fumigatus was confirmed by polymerase chain reaction. A multimycotoxin method was developed to quantify seven mycotoxins (aflatoxin B(1), alternariol, fumonisin B(1), gliotoxin, ochratoxin A, T-2 toxin, and zearalenone) in oilseed cakes by high-performance liquid chromatography coupled to mass spectrometry. Among 34 fungal species identified, A. fumigatus and Aspergillus repens were observed during 5 and 4 months, respectively. Gliotoxin, an immunosuppressive mycotoxin, was quantified in oilseed cakes up to 45 microg/kg, which was associated with the presence of toxigenic isolates of A. fumigatus.