Amorphous and crystalline Ti oxide films were obtained by reactive magnetron sputtering onto substrates at different temperatures. Optical constants of the films were determined from spectrophotometric measurements of reflectance and transmittance. The amorphous films had a band gap of approximately 3.4 eV and a wide absorption tail extending to lower energies. The crystalline films displayed a band gap of 3.3-3.35 eV and a more narrow absorption tail. The optical constants were dependent on film thickness. The crystalline films showed evidence of structural inhomogeneities leading to diffuse scattering in the thicker films as well as to a grading of the refractive index.