A two-step gas treatment of commercially pure titanium (CP Ti) was investigated with a focus on the formation of the anatase phase. The first step was carried out in Ar-l%CO atmosphere at 1073 K for 0 ks or in N2 atmosphere at 1123 K for 14. 4 ks. The subsequent second step was carried out in air at 473-873 K for 0 ks and 86. 4 ks. A titanium oxycarbide (TiC 1-xOx) layer was formed after the first-step treatment in Ar-1% CO atmosphere, and an anatase-rich TiO2 layer was obtained after the second-step treatments in air at 673-873 K for 0 ks and at 573 - 773 K for 86. 4 ks. In particular, single-phase anatase formed under the condition of the second step in air at 573 K for 86. 4 ks. The anatase fraction in reaction layer could be controlled by varying the temperature and holding time of the second step. Both the TiN and Ti2 N phases were detected as reaction products after the first step in N2 atmosphere, and an anatase-containing TiQ2 layer was obtained after the second-step treatment in air at 723 K for 86. 4 ks. The formation of TiN and its oxidation at low temperatures seem to be required for the preparation of an anatase-containing TiO2 layer on Ti.