ITO layers with low resistivity and high visible transmittance were produced by means of middle frequency reactive dual magnetron sputtering. The influence of base pressure, Ar/O-2 ratio and magnetron pulse duration on the film composition, structure, electrical, and optical properties has been investigated. The deposition rate is proportional to the magnetron operation power at changing pulse duration and constant Ar and O-2 flows. At enhanced O-2\ flows an onset of the magnetron target oxidation is discussed as a reason for the decrease of the deposition rate. The presence of water vapor in the residual gas is determined to be a reason for deterioration of resistivity and optical transmittance observed for ITO films produced at a base pressures higher than 5 (.) 10(-4) Pa. It is demonstrated that spectroscopic ellipsometry can be used as a noncontact tool to monitor the resistivity of ITO films. (C) 2004 American vacuum Society.