1. A total of 108 erythrocyte protoporphyrin determinations has been made in 66 normal individuals. The geometric mean ± standard error of the mean was 31 (26-38).

2. A total of 196 determinations of plasma iron in 92 normal individuals was made. The mean ± standard error of the mean was 104.7 ± 3.4 µg per cent.

3. In a total of 150 determinations of plasma copper in 105 normal individuals, the mean ± standard error of the mean was 118.6 ± 1.2. µg per cent.

4. No significant difference in plasma iron was noted between the sexes but in females the plasma copper was significantly higher and the erythrocyte protoporphyrin slightly higher than in males.

5. Erythrocyte protoporphyrin, plasma iron, and plasma copper determinations have been made in over 112 patients with a variety of clinical conditions associated with anemia. In general, it was found that in pernicious anemia in relapse the erythrocyte protoporphyrin values were normal, the plasma iron normal or high and the plasma copper usually normal. Anemia due to iron deficiency as well as the anemia of infection were accompanied by high values for erythrocyte protoporphyrin, hypoferremia and hypcrcupremia. In nephritis with anemia the erythrocyte protoporphyrin was generally increased, the plasma iron low or normal and the plasma copper increased. Anemia associated with lymph node disorders or leukemia was accompanied by a normal or high EP, a low or normal plasma iron and an increase in plasma copper. Thalassemia major was found to be accompanied by both hypercupremia and hyperferremia; in thalassemia minor the serum iron values were normal although hypercupremia was found. Hyperferremia was noted in aplastic anemia. In cases of plumbism the erythrocyte protoporphyrin was markedly increased. Hypocupremia was noted only twice, in one patient with severe nephritis and hypoalbuminemia and in one patient with hemochromatosis.

ACKNOWLEDGMENTS For samples of plasma from patients with thalassemia we are indebted to Drs. W. N. Valentine, Rochester, N. Y., P. Sturgeon, Los Angeles, and L. K. Diamond, Boston. The following gave valuable technical assistance: Misses Mary Iles, Betty Tatting and Wanda Worth.