Polycrystalline In2O3:Sn (ITO) films with thickness between 40 nm and 1.7 mum were prepared by direct current magnetron sputtering at 300degreesC substrate temperature. They were characterized by X-ray diffractograms; and transmittance curves. In the range of 0.4 to 1.4 mum, the films exhibit a mass density close to the crystalline value, small lattice distortion and microstrain, similar texture of crystalline orientations, high free electron density and low electrical resistivity. Films thinner than 0.4 mum do not exhibit such favorable properties. For all films, grain size and free carrier density decrease with increasing lattice distortion. We attribute the differences in the properties of the thin and thick films to a change of the film's microstructure taking place at 0.3-0.5 mum with more additional oxygen incorporated into the thinner films. (C) 2004 Elsevier B.V. All rights reserved.