Room-temperature ferromagnetism (RTFM) is observed in the bulk CoxTi1-xO2-delta (0.06 <= x <= 0.1) samples synthesized by the solid-state reaction method for the mixed powder of Ti and Co oxides, followed by a 500 C furnace annealing process in a 10% hydrogen-argon mixture of ambient gases. The X-ray diffraction, X-ray photoelectron spectroscopy, and measurements of magnetic susceptibility, x, vs temperature, T, indicate polycrystalline Co-doped TiO2 anatase without Co clusters was fabricated. A phase transformation from CoTiO3 to CoxTi1-xO2-delta occurs after the hydrogenation process. These results are strong indications for formation of oxygen vacancies near the high spin Co2+ sites, and the formed oxygen vacancies are essential for the generation of RTFM in CoxTi1-xO2-delta. Based on these observations, ferromagnetism in bulk CoxTi1-xO2-delta anatase could be attributed to the exchange interaction between Co2+ mediated by oxygen vacancies near Co2+ sites, not being caused by Co clusters. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.2130263] All rights reserved.