<p>The fungal genus Alternaria contains both saprophytic and pathogenic species. As plant pathogens, they cause serious problems in agriculture, reducing crop productivity and deteriorating fruit storage. Species of this genus can also be mycotoxicogenic, able to colonize crops and accumulate in infected products, secondary metabolites that can affect human and/or animal health. In the present work, apple (Malus domestica) and pear (Pyrus comunnis) fruits were sampled in three localities of the Alto Valle del río Negro (Cipolletti, General Roca and Villa Regina), in order to determine the presence of species of the genus Alternaria associated with these crops in the region. A total of 267 isolates belonging to the genus Alternaria were obtained. They were identified by their morphological characteristics (Simmons, 2007) as being equal or similar to Alternaria tenuissima, in a higher proportion (85 %). Also, A. mali and A. gaisen, host-specific species of apple and pear, respectively, were identified. The importance of the present study is due to the fact that it allows to consider the risk to the health of local crops because of this pathogen, and to evaluate the possibility of the presence of mycotoxins in infected fruits, which could reach the production chain, would be a risk to the health of the consumer.</p>