The American Academy of Pediatrics is committed to the use of maternal breast milk as the ideal source of nutrition for infant feeding. Even so, by 2 months of age, most infants in North America are formula-fed. Despite limited indications, the use of soy protein-based formula has nearly doubled during the past decade to achieve 25% of the market in the United States. Because an infant formula provides the largest, if not sole, source of nutrition for an extended interval, the nutritional adequacy of the formula must be confirmed and the indications for its use well understood. This statement updates the 1983 Committee on Nutrition review and contains some important recommendations on the appropriate use of soy protein-based formulas.