Indium tin oxide (ITO) films have been prepared by radio-frequency (r.f.) magnetron sputtering an oxide target (90 wt.% In2O3-10 wt.% SnO2) onto glass substrates without in-situ substrate heating. The effect of sputtering conditions on the deposition rate and the optical and electrical properties of ITO films are investigated. The as-deposited films have an electrical resistivity of approximately 4 x 10(-4) OMEGA cm, visible transmittance of about 85%, and infrared reflectance of above 80% at 5 mum. A virtual source of the sputtered particles is formed in the gap between the target and substrate and its position is related to the energy of the sputtered particles. The position of the virtual source is used to explain the correlation between the deposition rate and target-to-substrate distance. The O/In atomic ratio is found to decrease with increasing sputtering power, resulting in an increase in the carrier concentration of the film and a decrease in the Hall mobility. Blackening of ITO films deposited at high sputtering power is observed and discussed.