Breast-feeding protects the newborn against infectious diseases in developing as well as in industrialized countries. Protection is conferred against gastrointestinal and respiratory tract diseases as well as against otitis media. This protection provided by specific (antibody dependent) and broad, nonspecific protective factors in human milk (proteins, glycoproteins, and lipids) is associated with lower global morbidity and mortality of breast-fed infants as compared with formula-fed infants. While protection against diseases that develop later in life, such as insulin-dependent diabetes mellitus, inflammatory bowel disease, and childhood cancer, has been reported, well-planned prospective studies are essential in order to confirm these observations. Similar studies are essential in order to ascertain the small but consistently reported higher cognitive ability of breast-fed infants.