1. The adult possums showed a circadian rhythm of body temperature with a peak in temperature around midnight and a nadir at noon. 2. The young possum within the pouch displayed a circadian rhythm with the highest temperatures during the day and the lowest in the early evening. 3. Although the body temperature of the young possum exceeded that of the mother occassionally, for the major part of the 24 hr the body temperature of the young was lower than that of the mother. 4. The young possum could maintain a steady body temperature between 140 and 167 days post partum. A circadian rhythm of temperature was observed between 157-190 days post partum. 5. All adipose tissue examined with the light and electron microscope had the morphology of white adipose tissue.