The author has investigated the oxygen consumption in various regions of normal rabbit bone marrow by using Warburg's manometer. The results obtained can be summarized as follows: 1. In the long bone group, the oxygen consumption was greatest in the femur, followed by the humerus, tibia and radius in the order mentioned. The value was slightly greater in the epiphyseal part than in diaphyseal one, but stochastically no significant difference could be found between the diaphysis and epiphysis of both the femur and humerus. Of the 15 sets of comparisons made at six diffesent parts, namely, the diaphyseal and epiphyseal parts of the femur and humerus, and the tibia and radius, ten sets showed significant differences. 2. The O(2)-consumption was slightly greater in the hip-bone than in the scapula (in the flat bone group), but no significant difference could be found between the two values. Both bone marrow showed lower values than the diaphyseal part of the femur, and significant differences could be found between the two and diaphyseal part of femur, respectively. 3. The ether-extractable substances in the bone marrow of the long bone group showed the highest value in the radius. 4. In general there was a tendency showing a higher oxgen consumption of the bone marrow in winter than in summer; and significant differences could be found between the values in summer and in winter in the diaphyseal part of the femur.