Abstract. The world grape production has increased, reaching 751 million quintals (Mql) in 2013. Many Alternaria species have been studied for their ability to produce secondary metabolites in foods, some of which have toxic properties with tenuazonic acid (TA), alternariol (AOH), alternariol methyl ether (AME) being the most important ones. The aim was to determine the characteristic mycotoxin production profiles of Alternaria strains isolated from Malbec grapes in the Patagonian region of Argentina. Fifty Alternaria isolates (5 A. alternata, 5 A. arborescens and 40 A. tenuissima) were analyzed for the production of mycotoxins (TA, AOH and AME) in autoclaved rice media by High Performance Liquid Chromatography (HPLC). All isolates were found to be producers of mycotoxins; the 100% was producer of TA (0.016-21.031 mg/kg), 98% produced AOH (0.003-0.057 mg/kg) and 36% produced AME (0.001-0.133 mg/kg). Thirty-three isolates co-produced the three mycotoxins. In this study, it was demonstrated a high toxigenic potential of Alternaria isolates. Although Alternaria growth on grapes has been amply demonstrated, there are few studies about the incidence their more characteristic mycotoxin sand their toxicogenic capacity determination in grapes, wines and derivatives. In addition, mycotoxins studied in this work are not regulated in oenology. Therefore, further studies should be conducted to assess the health risk due to the presence of Alternaria toxins in grapes, wine, grape juice and raisins.