Thin layers of indium tin oxide (ITO) were deposited onto glass substrates by RF magnetron sputtering with the pressure varying from 6 mTorr to 15 mTorr. The films were annealed in a reducing atmosphere at 500 °C for 30 minutes. Sheet resistance was determined by four-point-probe measurement. Resistivity, mobility, and carrier concentration were obtained by Hall effect measurements. Transmission of the films in the visible spectrum was determined by photospectrometry. The structure of the films was characterized by X-ray diffraction. X-ray photoelectron spectroscopy was used to determine the oxidation state of Sn, which was used to determine the fraction of active tin clusters. The effect of additional anneals was investigated. The results reveal that the lowest resistivity obtained was 1.69×10-4 Ω-cm at 9 mTorr and the highest transmittance of 90% was obtained after a second anneal. However, the second anneal decreased the mobility and conductivity for high sputter pressures.