The toxigenic potential of 144 Fusarium graminearum sensu stricto strains isolated from wheat in different subregions of the main production area in Argentina during 2001, 2003 and 2004 harvests was studied. The mycotoxin producing ability of the isolates was examined by Gas Chromatography with Electron Capture Detection and confirmed by Mass Spectrometry. Analysis of the trichothecene chemotype distribution across the Argentinean wheat cropping area revealed that 15-acetyldeoxynivalenol was the most common chemotype. Two other chemotypes, the 3-acetyldeoxynivalenol and 3- and 15-acetyldeoxynivalenol, were always present. The number of isolates with simultaneous production of both acetylderivatives increased along the years. The frequency of isolates with different toxigenic profile did not shown significant differences by subregions. An increased vigilance over crop seasons and geographical areas should be carried out to detect changes in the chemotypes distribution.