This case control study evaluates the association between hospitalization due to infection and feeding practices among infants aged >or= 3 days to < 6 months. Mothers of 191 cases hospitalized for infections and 208 healthy controls were interviewed using a standardized questionnaire documenting infant-feeding history. Results given in odds ratio and 95% confidence intervals (OR, 95% CI) were adjusted for age, education, and place of delivery. Exclusively formula-fed infants were more likely to be hospitalized for any infection (3.7, 1.8-7.5), pneumonia (3.0, 1.2-7.4), and diarrhea (10.5, 2.5-41.9) compared to exclusively breastfed infants. Infants who did not receive any breast milk were more likely to be hospitalized for any infection (3.5, 2.1-5.9), neonatal sepsis (4.9, 1.3-18.3), pneumonia (2.8, 1.5-5.4), and diarrhea (19.6, 6.5-58.6) than infants who received any breast milk. This study showed a strong positive association between the intake of formula and/or nonbreast milk supplements and the risk of hospitalization for infectious causes.