Infant formulas typically come fortified with iron to prevent iron-deficiency anemia. A new study of 494 Chilean children showed that those who received extra-iron fortified formula in infancy lagged behind those who received lowiron formula in cognitive and visual-motor development by the age of 10 years. In this study, most children who received the 12 mg formula showed higher scores. However, the 5% of the sample with the highest hemoglobin levels at 6 months showed the poorest outcome. Adversely affected children scored lower in IQ, visual-motor integration and spatial memory. This study suggests that extra iron (with formula) for infants who do not need it may delay development. Anahtar Kelimeler : iron, supplements, formula, cognitive