The clinical manifestations in 595 children hospitalized with gastroenteritis during a 15-month time frame were studied. They were divided into eight groups according to etiologic agent: rotavirus (203 patients); Salmonellae (98); Escherichia coli (55); Campylobacter (36); Shigella (22); combined rotavirus and salmonellae (44); combined rotavirus and other bacteria (26); and no pathogen (111). The mean duration of diarrhea was shortest in the rotavirus and "no pathogen" groups (4.8 and 5.6 days, respectively) and longest with pure and mixed salmonella infections (12.3 and 12.9 days, respectively). Associated manifestations were most frequent with salmonellae and least frequent with rotavirus and E. coli infections. Malnutrition also was most common with salmonellae and lowest with rotavirus and E. coli. There were no differences in the frequency of hypernatremia. Hyponatremia was most frequently encountered with salmonella (25% compared to 9% in the rest of the patients). Evidence of septicemia was found in 22 patients, 21 of whom were in the salmonella groups. The four deaths in this series (0.7%) also were in the salmonellae groups. The clinical severity of salmonella infection in developing countries, particularly in young and malnourished children, warrants attention to more intensive management. The selective use of antibiotics may help reduce the mortality and morbidity of gastroenteritis.