Calorimetric heats of adsorption have been determined for sulfur dioxide adsorbed at 298, 323, 373, and 423 K on both Californian and Quebec chrysotiles. Adsorption isotherms have been measured and some differential molar entropies calculated. Thermal desorption of surface species resulting from the adsorption of sulfur dioxide on Californian chrysotile at 298 K have been studied from 25 to 450 °C. Sulfurous and carbonic acids, in addition to sulfites and other trace species, have been shown to result from the adsorbent–adsorbate interactions. A mechanism for sulfur dioxide adsorption on chrysotile has been prepared which accounts for the observed high heats of adsorption measured at low surface coverages.