Summary1. One hundred and twenty‐five ill infants and children who were found to have iron‐deficiency anaemia were treated with in tramuscular iron‐dextran complex with doses varying from 100 to 400 mg, con‐current with treatment for the presenting illness.2. The mean haemoglobin levels before treatment ranged from 8.91 g%to 9.61 g%in the various age groups; at 3 weeks after the injection of iron the mean haemoglobin levels were found to range between 10.12 g%and 10.80 g%and at 6 weeks after injection the mean haemoglobin levels had risen further to range between 10.75 g%and 12.0 g%. There was thus an approximate general rise of 2 g %of haemoglobin in 6 weeks. Clinically the beneficial effects were quite striking, and occurred often within days.3. The results of this investigation indicate that intramuscular iron‐dextran complex can significantly raise the haemoglobin level in infants and children who have iron‐deficiency anaemia with a variety of associated illnesses, of all degrees of severity, and of largely undetermined duration. In addition, iron‐dextran complex was found to be safe and easy to administer.4. The factors influencing rate of recovery from iron‐deficiency anaemia after in tramuscular iron‐dextran complex, the theoretical dangers of iron overload and the possible production of sarcomata in iron‐injected t