Thin films of TiO2-x with reproducible optical and structural properties were deposited by d.c. reactive magnetron sputtering. The automatic control of the sputtering conditions was attained by monitoring the emission line of metallic Ti at lambda = 500 nm and by using this signal as a feedback to operate the gas admission system. Grazing incidence diffraction (GID) revealed formation of the anatase-rutile mixtures in all deposited films. Spectrophotometric measurements showed a shift in the fundamental absorption edge from 3.4 to 3.2 eV that could be traced back to the diminishing amount of the anatase phase in films deposited at high sputtering rates. The change in the refractive index from 2.3 to 2.45 was also observed.