Although biochemical evidence seems to support the fact that more DHA is incorporated into the brain of breastfed infants compared with formula-fed infants, whether the levels of DHA in the brain are clinically significant is unclear. Because randomized trials cannot be done, this issue is difficult to study. The effects of breastfeeding on developmental outcome in term infants seems to be small or insignificant. For otherwise healthy children the potential differences are not clinically relevant; however, these small differences distributed over an entire population might have a significant effect on society. Although significant methodologic concerns exist, the effects of breastfeeding on preterm infants may be greater than those for term infants. Extremely low birth weight, premature infants (< 750-1000 g) have been found to have IQs that are 13 points lower than term controls and a 50% to 60% risk for requiring special-education services when they are in school. In these infants, small improvements in IQ and neurologic function could have a much greater effect. Further study of neurodevelopmental outcome in premature infants fed breast milk compared with those fed preterm formula are indicated. This information should not change the practice of encouraging breastfeeding of term and preterm infants because other advantages to breastfeeding exist.