A study was made of the effects on O2 consumption of halogenated salicylates in normal, thyroidectomized and hypermetabolic rats. It was found that 5-iodo-2-hydroxybenzoate and 5-bromo-2-hydroxybenzoate increased the metabolism of rats under these 3 conditions. 4-Iodo-2-hydroxybenzoate increased the metabolism of normal and thyroidectomized rats. 5-Iodo-2-hydroxybenzoate and sodium salicylate increased the metabolism of normal mice. 3,5-Diiodo-2-hydroxybenzoate, 5-iodo-3-hydroxybenzoate and 3-hydroxy-benzoate did not increase the metabolism of rats.