The medical history for the first year of life of 106 infants in a rural community was reviewed. During the first month of life, a significant difference was found in the number of office visits for illness between breast-fed infants and infants who were bottle-fed from birth. For the first 6 months of life, breast-fed infants with and without bottle supplements had significantly fewer months with illness than bottle-fed infants, regardless of prior exposure to breast milk. Demographic data indicated no appreciable differences between feeding groups. It is concluded that breast-feeding offers a protective advantage against illness.