The etiology of diarrhea in children <5 years of age in a low-income housing project in Bangkok, Thailand, was determined over 1 year. Nontyphoidal salmonella (13%), Campylobacterjejuni (12%), rotavirus (12%), enterotoxigenic Escherichia coli (7%), shigellae (6%), E. coli that hybridized with the enteropathogenic E. coli adherence factor probe (3%), and enteroinvasive E. coli (1%) were identified in 345 episodes of diarrhea in children <5 years of age. Salmonellae were identified in 17% and C. jejuni was identified in 15% of 54 children <6 months of age with diarrhea. Shigellae, enteroinvasive E. coli, enteropathogenic E. coli adherence factor, and enterotoxigenic E. coli were not isolated from children <6 months of age. Since salmonella and C. jejuni were the most common bacterial pathogens identified in children <6 months of age, efforts to prevent transmission of salmonella and campylobacter to young children should be a public health priority in Bangkok.