After having injected into rats intramuscularly the serum of patients of hypoplastic anemia, the author made an attempt to study the adrenal cortical function of this disease, and the following results were obtained. 1. After the first injection there appeared a decrease in the number of circulating eosinophils, and while with successive injections once a day, 5 or 10 days, there occurred a similar decrease of eosinophils, but on stopping injections there appeared a remarkable increase of eosinophils. 2. The decrease in the number of circulating erythrocytes were observed in all cases, without any relation to the time of injections. This fact proved the existence of anemia producing factor in the sera of patients with hypoplastic anemia used in the present experiments. 3. After the first injection, a remarkable increase in the amount of free chemocorticoids (Ch. C.) excreted in the urine indicated that adrenal cortex was hyperfunctioned; with the progress of injections, of over 5 times, a gradual decrease of Ch. C. in the urine indicated that adrenal cortex was hypofunctioned. After stopping successive injections there occurred a remarkable increase of Ch. C. in the urine. 4. After the first injection there was no change in P(32) uptake into any organs. By successive injections an increase in P(32) uptake into hypophysis, bone marrow, liver and spleen can be observed. P(32) uptake into adrenals increased after the last injection, but it became normal 5 days after the cessation of injections. 5. Reserve function of adrenal ccrtex was maintained well even after the successive injections.