The effect of dexamethasone (DEX) and corticosterone (COR) on the activity of monoamine oxidase (MAO), copper-zinc superoxide dismutase (CuZn SOD) and manganese superoxide dismutase (Mn SOD) in the rat interscapular brown adipose tissue (IBAT) were studied. DEX (1 mg/kg, i.p. for two days) significantly increased MAO activity in the IBAT as compared to the corresponding controls. On the contrary, COR, in the corresponding dose (5 mg/kg), did not affect MAO activity in the IBAT. DEX also markedly enhanced the activity of both SODs in the tissue studied, while COR was ineffective. The results suggest that there exist the differences in the effect between the synthetic glucocorticoid, such as DEX, and COR, which is a natural glucocorticoid in the rat, on the activity of IBAT enzymes studied.