Salmonellosis in older children and adults is usually a self-limited disease, but the risk of complications in infants is not well-defined. We performed a retrospective review of 52 patients. 90 days of age or less, seen at the St. Louis Children's Hospital between 1975 and 1981 with stool cultures positive for salmonella. Sixteen were 30 days old or less (neonates), 21 were 31- 60 days of age, and 15 were 61-90 days old. Among patients in whom blood cultures were done initially, bacteremia was most frequent in neonates: 5/11 (45%), compared to 2/18 (11%) in older infants. All seven infants presenting with bacteremia received 10 or more days of antibiotic therapy: yet complications (osteomyelitis, fatal meningitis or chronic diarrhea) developed in three of five neonates and one of two older infants. Complications also developed in seven of 22 patients who initially had negative blood cultures, including two infants in whom sepsis later developed and two infants who required intravenous hyperalimentation because of chronic diarrhea and malnutrition. The group of 23 patients who did not have blood cultures all did well. Salmonellosis is not necessarily a self-limited infection in young infants. Even in the absence of bacteremia, clinicans would appear to be justified in using antimicrobial therapy in infants 3 months of age or les with salmonella gastroenteritis, particularly neonates of older infants with symptoms of dysentery or failure to thrive.