The simultaneous adsorption of SO2 and NOx on Na-gamma -alumina was studied by means of step experiments in a fixed bed plug flow reactor at 387 K and atmospheric pressure. Typically the molar composition of the feed gas was 1.5% SO2, 1% O-2, 4000 ppm NO, 500 ppm NO2, and Ar. First the adsorption behavior of the pure components was measured. SO2 and NO2 adsorb easily, whereas NO and O-2 do not adsorb. Moreover there is no influence of O-2 On the adsorption behavior of the pure components. NO and O-2 adsorption require the simultaneous presence of SO2 NO, and O-2. The NO and O(2)adsorption rate is enhanced by an increasing SO2/NO ratio. The total amount of SO2 adsorbed is not affected by the simultaneous adsorption of NO and O-2 However, NO2 adsorption increases the SO2 adsorption capacity. In the presence of NO2 most of the adsorbed NO, is released as NO.