An etiological study of bacterial diarrhea in infants under five years of age in Paraguay from May to July of 1990 was done. Enteropathogenic E. coli (EPEC) strains of known serogroups were isolate from 35.8 percent of the patients with diarrhea, Salmonella spp. were isolated from 15.1 percent , enterotoxigenic E. coli (ETEC) strains were isolated from 5.7 percent, and Shigella and Campylobacter spp. were isolated. Out of 53 diarrheal patients, 34 cases (64.1 percent) had bacterial diarrheal disease. The infants under one year of age with diarrhea were predominant among impatient and outpatient children under five years of age and the total number of male diarrheal cases was greater than that of female cases. Enteropathogenic organisms were isolated from nine out of 12 water samplestaken from the Paraguay River. The major serotype (O18) of the EPEC isolated from the water samples of the Paraguay River correspond to the mayor serotype isolated from patients with diarrhea