Newborn infants born after a term gestation appear to have an adequate capacity for small intestinal digestion and absorption of carbohydrate. Premature infants do not have a mature level of intestinal lactase activity. Apparently, in the premature infant, colonic fermentation serves an important, if not the only major route, for lactose carbon absorption, and it also appears that signs of fermentation activity such as increased BH2 are not indicative of disease. Important questions remaining in the premature infant relate to developmental aspects of colonic fermentative activity, effects of systemic antibiotic treatment on colonic salvage, the effects of various fermentation pathways on energy balance, the capacity for absorption of sugars, SCFA, and electrolytes by colonic epithelia, and the effects of fermentation products on metabolism and on the mucosal cells of the intestine or colon. Research addressing these questions may have relevance in the following areas: further development of formula diets for healthy premature infants and for patients of all ages with intestinal or colon dysfunction; the effects of colonic disease or surgical resection; the nutritional or clinical effects of dietary fiber; and the effects of antibiotic therapy on intestinal and colon function.