The composition of specialized formulas for infants who experience malabsorption or formula intolerance is described in detail. The limited studies of efficacy, as well as a rationale for selecting an appropriate formula for infants with malabsorption or formula intolerance, are discussed. Infants with symptoms of diarrhea or emesis may have intolerance to milk lactose or milk protein. Soy formulas contain no lactose or cow's milk and should be the first choice of an alternative feeding because of cost and convenience. Some infants may be intolerant of soy as well as cow's milk protein. They benefit from formula containing neither cow's milk nor soy protein or from a specially processed milk-based formula containing hydrolyzed casein. A carbohydrate-free formula to which the desired type of carbohydrate is added may be helpful in the diagnosis and treatment of disaccharidase deficiencies and monosaccharide intolerances. Infants with extensive intestinal resections or intractable diarrhea may require specialized infant formulas with qualitative/quantitative modifications of fat, carbohydrate, and protein. Formulas with medium-chain triglycerides may be useful for infants with steatorrhea. "Preterm" formulas or milk from the infant's mother are preferred for preterm infants, since such feedings promote improved fat and carbohydrate absorption and better meet the infant's nutrient requirements.