This work refers to the main electro-optical characteristics exhibited by large area indium tin oxide films (300 x 400 mm) produced by r.f. magnetron sputtering under different oxygen concentrations and deposition pressures. Besides that, the ageing effect on the electro-optical characteristics of the films produced was also analyzed. The results achieved show that the film transparency and conductivity were highly improved (more than four orders of magnitude) by first annealing them in air at 470 degrees C, followed by a reannealed stage under vacuum, in a hydrogen atmosphere, at 350 degrees C. The ageing tests show that film degradation occurs when the films are produced at oxygen concentrations above 10% and/or at deposition pressures above 1.2 x 10(-2) mbar.