Photocurrent performance and crystalline structures of TiOx films prepared by an Ar+ ion beam-assisted reactive deposition method were investigated. In this method Ar+ ion beam bombardment was carried out at 10 keV simultaneously during Ti evaporation in an oxygen atmosphere. The TiOx films obtained at an ion current density of 10-40 mu A cm(-2) showed a rutile-type crystalline structure, while the TiOx films obtained at an ion current density below 5 mu A cm(-2) showed a poor crystallized or amorphous structure. The latter TiOx films were photocatalytically inactive under 196.6 W cm(-2) Hg lamp illumination in a solution of 0.1 mol 1(-1) KHCO3. The maximum photocurrent density of 2.3 mA cm(-2) was obtained for the former TiOx films at an electrode potential of 1.5 V. However, this value was much less than that reported for the TiO2 films prepared by a sol-gel method (10 mA cm(-2)) having an anatase structure. Therefore, the photocurrent performance of TiOx films depends primarily on the crystalline structure.