The reaction between nanometer TiO₂ and CCl₄ in the presence of oxygen has been studied in order to investigate the potential of nanometer TiO₂ as a destructive reagent for chlorinated hydrocarbons. Two kinds of nanometer TiO₂ of different size were synthesized. The properties of the destructive adsorption of CCl₄ over nanometer TiO₂ of about 40 nm in size were compared with that over nanometer TiO₂ of about 80 nm in size. The reactivity toward CCl₄ of nanometer TiO₂ of about 40 nm in size was remarkably higher than that of nanometer TiO₂ of about 80 nm in size. The products produced included CO₂, COCl₂, Cl₂, titanium oxychloride, TiCl₄, carbon, CO and HCl. HCl was a major gaseous product. Hydrogen of HCl came from traces of water in the carrier gas and surface OH groups of TiO₂. The formation of TiCl₄ made the interaction surface renew so that CCl₄ could further interact with the bulk of the particles. TiO₂ was regenerated through the exchange of chlorine with oxygen at 550 °C in the carrier gas so that larger quantities of CCl₄ are decomposed over nanometer TiO₂ in the presence of oxygen. A mechanism has been proposed for the destructive adsorption and desorption of CCl₄ over nanometer TiO₂ in the presence of oxygen.