The aim of this study was to assess the effects of chronic iron deficiency on neuropsychological traits in infants. We established the nutritional iron status and assessed the neuropsychological characteristics of 58 Mexican 14- to 18-month-old infants. The Bayley Scales of Infant Development, preschool language scales and an environmental sound perception task designed expressly for the study, were used. The infants' mothers were asked to fill out 2 questionnaires concerning their child's sociodemographic background. Six different neuropsychological domains were analyzed. Results showed that the chronic iron deficiency group did show significantly lower scores on language, environmental sound perception, and motor measures, when compared with infants with normal nutritional iron status at 6 and 14 to 18 months. Our conclusion is that the development of language and motor skills and environmental sound perception appeared to be sensitive to the effects of chronic iron deficiency in infants.