Abstract 1. Catecholamine treatment at room temperature elevated the mitochondrial protein content and total activity of succinate dehydrogenase and cytochrome oxidase in adipose tissue of guinea-pigs, Cavia porcellus as did cold exposure, but changes were not so marked as in cold. 2. As with cold exposure the specific activity of cytochrome oxidase was increased but not that of succinate dehydrogenase by catecholamine treatment. 3. The specific activity of succinate dehydrogenase was, however, higher in the catecholamine-treated than in the cold-exposed animals. 4. The results show that exogenous catecholamine treatment had quite similar effects on the adipose tissue to those of cold, i.e. increased oxidative capacity of tissue.