In December 1979, an enzootic with a high rate mortality diarrhea in few days old calves, fed artificially, began on a rural farm, located in El Trébol (provincia de Santa Fe). Bacteriologic studies allowed the isolation of Escherichia coli from both blood and mesenteric lymph nodes. Symptoms were reproduced in two healthy calves injected with a toxin made from this bacteria. Autopsy of one of these calves revealed congestion and hemorrhagic disseminated in the intestinal mucus membrane together with infarcted mesenteric lymph nodes. This coli enterotoxicosis extended until March 1980, was the worst pathology affecting the farm during the last ten years (Tables 2, 3). The mortality from this enzootic increased six times as compared with four month period from 1970 to 1979, and it was doubled during January and March (Table 4). The predisposing factors that give rise to this illness and the bacterial etiology of which was demonstrated by experimental methods are discussed.