Up until to-day, it is generally believed that the metabolism of the corpulent person is essentially not different from that of the slender person. In order to elucidate as to whether a similar result is observed or not even when the variation in the metabolism due to the adaptation is taken into consideration, the author determined the gas metabolism and the various somatic functions at rest, and obtained the following results.<BR>(1) The basal metabolism and the metabolism at rest per body weight of the corpulent person demonstrated very much lower value compared with that of the slender person. However, no significant difference was noted in the value per body surface area.<BR>(2) Among the corpulent persons, especially those who recently became corpulent with relatively poor working ability, showed a low value, and those who recently became slender demonstrated a high value. Moreover, the values of the basal metabolism of the corpulent and slender persons who remained unchanged during these several years showed a reversed aspect in the difference compared with that stated in the above (1) . The high value in the metabolic rate demonstrated by the former is due to the higher cardiac function, espcially to the higher pulse pressure adapted to the prolonged continuous living conditions, and the lower value observed in the latter is considered to be due to the diminution of the cardiac function.<BR>(3) No qualitative differences were noted in the respiration quotient of the rest metabolism and its daily fluctuation between the groups of corpulent and slender persons examined.