Three adsorption isotherms of SO2 on ice were measured at -3¿,-11¿, and -30¿ C in the SO2 concentration range of 0.3 to 6 ppmV. The isotherms indicated that there is a strong increase of adsorption as the temperature rises toward the melting point. This behavior may correlate with the presence of a quasi-liquid layer on the surface of ice. If this behavior is typical of impurity adsorption on ice, it is important in the processes that govern the acquisition, transport and storage of atmospheric pollutants by snow.