Titanium dioxide, known in three different crystallographic forms (anatase, rutile and brookite) is one of the transition metal oxides that has received increasing interest in recent years, for various reasons (mainly, because of its role as a pigment), in order to improve its properties and to avoid its decay (due mainly to its ability to catalyse photoreactions under exposure to sunlight). It has also been the subject of research because of its role as a catalyst support for metallic oxides, as well as for oxide catalysts, due to its easy (and reversible) partial reduction to the TiO2n_l form. Rutile is the most stable form of titanium dioxide, and is commercially prepared [1] from titanium(IV) chloride. The pigmentary properties of calcined particles are known to be strongly influenced by the amounts of additives [2]. The presence of chloride as an impurity is difficult to avoid, because of the starting materials for manufacture, and it has been shown that the presence of this species strongly modifies other properties of the solid [3-6]. Garbassi et al. [7] have reported the effect of hightemperature treatments on the surface properties of doped rutile and anatase, but these authors have studied only the effects of several metallic cations (K +, Zn 2+ and A13+) and of P205. Removal of impurities in rutile has been explained on the basis of diffusion of the cations through the structure channels by an interstitial mechanism [8]. In this letter we report the changes (mainly surface properties) observed in commercial rutile when submitted to calcination under a humid atmosphere, a method that has been shown to be valid for removal of chloride species. Commercial rutile containing 9 wt % of chloride was kindly supplied by Tioxide Ltd (UK). It had been obtained by flame hydrolysis of titanium(IV) chloride, dried at 393 K and calcined at 673 K. In addition to chloride, all other impurities (P205, K20, CaO, A1203, SiO2, Fe, Pb, Nb2Os) were less than 100 ppm, except SO3 (220 ppm). X-ray diffraction (XRD) diagrams were recorded in a Siemens D-500 diffractometer equipped with a Difract-AT system and a DACO-MP microprocessor, using CuKo~ radiation. Specific surface area and texture measurements were carried out from nitrogen adsorption isotherms at 77 K. The samples were calcined at 773 K under an oxygen flow, saturated with water vapour at 308 K.