Iron deficiency causes different abnormalities in the three major population groups that are at risk. In pregnant women, epidemiological studies suggest that anaemia, presumably due mainly to iron deficiency, is associated with an increased risk of low birth weight, prematurity, and perinatal mortality. In iron-deficient infants and children, there is convincing evidence of impaired psychomotor development and cognitive performance. Finally, iron-deficient women during the childbearing years (and iron-deficient men) have a decreased work capacity and less efficient response to exercise. These symptoms provide ample justification for preventing and treating a common and easily correctable nutritional disorder.