Compensatory mechanisms in children with iron-deficiency anemia were evaluated by measuring erythrocytic organic phosphates and, in some cases, shifts in the P50 of the oxygen dissociation curve. In 19 children with nutritional anemia (hemoglobin values of 3.2 to 8.2 gm/dl) there was a calculated improved oxygen delivery to tissues equivalent to a hemoglobin level of at least 7.5 gm/dl. Transient decompensation was observed during acidosis. In five children with iron-deficiency anemia due to blood loss and in one child with rheumatoid arthritis no such compensatory changes were observed.