The iron requirement for breastfed infants remains controversial. Given the impact of iron on neurodevelopmental outcomes and the questionable impact of iron supplements after iron deficiency has occurred, its importance as a nutrient in this population cannot be down played. Infants are born with relatively large body stores of iron that are marginally related to maternal iron status in developed countries. Delayed cord clamping may increase these fetal stores, but at the present time this is only recommended for preterm infants who are born with low iron stores. The diagnosis of iron deficiency (ID) and iron deficiency anemia (IDA) remains problematic though new laboratory tests (measures of reticulocyte hemoglobin concentration and serum transferrin receptor) hold promise in developed countries. The present evidence supports the potential benefits of iron supplementation of exclusively breastfed infants after 4 months of age, by which time the iron stores present at birth are depleted. This deficit cannot be made up even if the small amounts of iron in human milk are completely absorbed.