Anemia of prematurity is characterized by low reticulocyte counts and inadequate erythropoietin response, for which many premature infants receive multiple blood transfusions. To reduce the number of those transfusions, treatment with EPO and iron supplementation is routinely used in premature infants. Even if the efficacy of this treatment is demonstrated, the results are not so good in the very low birth weight infants or very small gestational age infants and the need of transfusion is still important. This is due for a large part to blood loss in these very small infants. But there are also other explanations. Thus the pharmacokinetics of EPO is different in premature infants and newborn than in adults. Best dose, best way of administration (i.v. or subcutaneous), best number of injections per week are not already known. Further study has to be done to achieve a better use and efficacy of this treatment.