Although the American Academy of Pediatrics and the American Academy of Family Physicians recommend breast milk for optimal infant nutrition, many parents still choose formula as an acceptable alternative. The wide variety of available formulas is confusing to parents and physicians, but formulas can be classified according to three basic criteria: caloric density, carbohydrate source, and protein composition. Most infants require a term formula with iron. There is insufficient evidence to recommend supplementation with docosahexaenoic acid or arachidonic acid. Soy formulas are indicated for congenital lactase deficiency and galactosemia, but are not recommended for colic because of insufficient evidence of benefit. Hypoallergenic formulas with extensively hydrolyzed protein are effective for the treatment of milk protein allergy and the prevention of atopic disease in high-risk infants. Antireflux formulas decrease emesis and regurgitation, but have not been shown to affect growth or development. Most infants with reflux require no treatment. Family physicians can use these guidelines to counsel parents about infant formula, countering consumer advertising that is not evidence-based.