1. The anemia of civilian trauma (mainly limb injuries) has been studied in 57 patients.
2. In 22 patients the red cell volume, after primary blood loss has probably ceased, has been compared with the follow-up "normal" red cell volume. The red cell volume credit or deficit is taken as an index of the balance between primary blood loss and blood transfused, and was found to be the major factor contributing to the later polycythemia or anemia. The evidence suggests that an anemia of trauma due to unreplaced primary blood loss is still a common finding in civilian injuries today.
3. A further red cell volume estimate in 20 patients on the 4-14th day after injury showed on average a further fall of 11 per cent of the red cell volume. Evidence is presented for considering that there is a further disappearance of red cells after primary blood loss has ceased in all patients—even in those whose red cell volume did not fall.
4. The evidence suggests that the anemia of trauma is largely preventable by adequate blood transfusion in the majority of civilian injuries.