The pediatric health care provider is often faced with myriad decisions related to the use of infant formula. This article compares human milk to cow's milk. It addresses the composition, classification, and use of some of the most common infant formulas manufactured for use with the term infant in the outpatient setting. Common clinical situations are discussed, including the role for low-iron, goat's milk, and follow-up formulas, and formula use for the Infant with diarrhea, colic, and atopic disease. The article highlights the poor quality of research and the lack of definitive answers available to the clinician when managing the Infant with atopic disease. It concludes with a review of practical aspects of infant formula feeding for use in client education and management, including guidelines for formula preparation, calculating necessary formula intake, frequency, and quantity of Infant feedings, and provisions of the WIC program.