Abstract 1. The injection of the β blocker propranolol reduced the rise in oxygen consumption which normally occurs in neonatal pigs exposed to cold. 2. Propranolol also reduced the plasma concentration of FFA. 3. The reduction in oxygen consumption cannot be due to the blockage of the action of noradrenaline on brown fat because this issue used as a substrate in non-shivering thermogenesis in some other tissue.