1) Following the classification of Prof. Hiraki the author divided hypoplastic anemic patients into five types and carried out the following studies. Oxygen consumption and glycolysis of the sternal bone marrow aspirated from hypoplastic anemic patients generally showed a decrease but the degree of the decrease varied according to the type of anemias, namely, the type of blood cell arrest showed the value close to that of the normal person, followed by type of maturation arrest and type of regeneration disturbance, and mixed form as well as type of pan-myelophtisis showed markedly low values. 2) The oxygen consumption (i.e. O(2)-consumption values) of peripheral erythrocytes of hypoplastic anemic patients was recognized to be lower than that in the normal person. Moreover, it was found that the in vitro addition of various substances that reactivate the respiratory action of erythrocytes showed lower values in oxygen consumption of erythrocytes of hypoplastic anemic patients. 3) It has been proved that the serum of hypoplastic anemic patient in vitro has an inhibitory action against the O(2)-consumption of erythrocytes of normal persons.