We identified children with alpha 1-antitrypsin deficiency from the medical records of the Massachusetts General Hospital and Children's Hospital, Boston, and investigated their early feeding history. Between 1969 and 1983, forty children with the deficiency were seen at one or both hospitals. Clinical information was obtained from hospital records and from questionnaires mailed to the parents. Complete morbidity, mortality, and early feeding data were obtained for 32 of the children who were born at 38 to 42 weeks' gestation and whose weights were appropriate for gestational age. We compared the presence of severe liver disease and the death rate of those who had been exclusively breast-fed for one month with those who had been bottle-fed. Severe liver disease was present in eight (40%) of bottle-fed and one (8%) of breast-fed infants. Twenty-four of the 32 infants were still alive at the termination of the study; 12 had been breast-fed and 12 bottle-fed during their first month of life. All eight deceased infants had been bottle-fed. The mortality rate in the bottle-fed group was significantly greater than that of the breast-fed group. Our study suggests that breast-feeding may offer some protection against severe liver disease and early death in infants with alpha 1-antitrypsin deficiency.