Epitaxial thin films of (001)-oriented FeTiO3+delta were prepared on alpha-Al2O3(001) single crystalline substrates by helicon plasma sputtering technique. The FeTiO3+ films had large oxygen nonstoichiometty, which seriously depended on both substrate temperature and oxygen pressure during the sputtering deposition. The valence states of Fe ions in FeTiO3+delta changed monotonically from Fe2+ to Fe3+ with decreasing the substrate temperature from 900 to 400degreesC or with increasing the oxygen pressure from 0.9 to 1.8x10(-6) Pa. ne change of Fe valence states from Fe2+ to Fe3+ induced the magnetic phase transition only for the films prepared at 900degreesC. The films containing Fe2+ were paramagnetic while those with Fe3+ were antiferromagnetic at room temperature. The oxygen nonstoichiometry of the FeTiO3+delta films was probably produced by cation vacancies and disarrangement of Fe3+ and Ti4+ ions, which randomly occupied both interstitial and substitutional sites of the FeTiO3 related structure.