Unique immunological factors in breast milk are responsible for the protection it affords infants against pathogenic agents. This protection is particularly effective against the infectious agents which invade or colonize the small and large intestine. Factors interfering with enterotoxigenic and enteroinvasive bacteria, and with entero- and rotaviruses, have already been detected in colostrum and mature human milk. Moreover, the biochemical composition of human milk makes it the best infant food during the first 6 months of life, and with supplementation, for months thereafter. At the same time, optimal maternal-infant interactions are effected during breast-feeding which strengthen infant care in health, in illness and during convalescence. The low cost of breast-feeding when compared to other types of alimentation, coupled with its unparalleled nutritive, anti-infectious, and behavior stimulating properties makes it the main promoter of infant health. There remains a need for investigation of the factors that have brought about a reduction in breast-feeding throughout the world. New methodologies to increase the incidence of breast-feeding, particularly in the developing nations, are critical. The availability of such methodologies could facilitate delivery of other health interventions ideally delivered by the mother, the most important agent for improving the health of infants and children.