Diarrheic processes pose a grave health threat in much of Latin America, especially for small children. One reason for this is the close connection between diarrhea and lack of proper nutrition. The present article seeks to explore this connection by examining two of its main components: the protection against diarrhea resulting from breast-feeding and the increased vulnerability to diarrhea created by malnutrition. Breast-feeding helps prevent enteric infections in several ways. For one thing, the mother's colostrum and milk contain antibodies against some enterobacterial antigens. For another, the so-called "bifid factor" in human milk helps discourage growth of pathogenic enterobacteria in the intestinal lumen. Furthermore, children living in unhealthy surroundings become heavily exposed to common bacteria when breast-feeding stops, a circumstance deemed largely responsible for "weaning diarrhea." Proper nutrition in general is also important, since diarrhea tends to be more common and severe among malnourished children. Several processes that could contribute to this problem have been suggested. These include morphological alterations of the intestinal mucosa in malnourished children, poor intestinal absorption of fats and other nutrients, irritation caused by increased concentrations of free bile acids, and changes in the composition of the intestinal flora. Though not all these processes are well understood, it is clear that malnutrition favors development of diarrhea, while diarrhea in its turn precipitates and aggravates malnutrition. The sad plight of millions of children in the Americas is the result of this combined interaction. Many of those who experience it die, and the survivors fail to achieve their full potential growth and development. The control of diarrheic infections alone would greatly improve these children's nutritional status. Likewise breast-feeding in the early months of life, duly supplemented later and followed by a sound diet after weaning, would considerably reduce the danger and damage caused by diarrheic infections.