Authors present a prospective study upon 193 cases of acute gastroenteritis in infants 1 to 24 months of age, giving special attention to clinical evolution of the disease without any use of therapy of either antibiotics or other antidiarrheal agents. Data on epidemiology and etiology of this series are similar to those previously reported by other authors. Mean duration of diarrhea was 2,5 days, whereas mean hospital stay was 7,5 days. The number of cases of prolonged diarrhea was 13, from which six were cases of lactose intolerance, six were cases of cow's milk protein intolerance and one was a case of intractable diarrhea. The little use fulness of antibiotics in the treatment of acute diarrhea is commented and also a discussion is made of the different factors involved in the onset of the complications above mentioned.