Indium tin oxide (ITO) thin films were grown onto soda lime glass substrates by sputtering at room temperature. The structure, optical and electrical characteristics of the ITO layers have been found dependent on the film thickness, determined by the deposition time, and the oxygen partial pressure introduced in the sputtering atmosphere. After exposure of the samples to the damp-heat test, which applies 85 °C temperature and 85% relative humidity for 1000 h, no degradation of the film properties has been detected except for the layers prepared at the highest oxygen flow that showed a sheet resistance increase about 14–20% after the 1000 h treatment.