The structural and electrical properties of indium tin oxide (In2O3/SnO2) thin films grown using direct evaporation technique on various substrates at different temperatures were studied. The effect of annealing, of films with different weight percent concentration of SnO2 in In2O3 and of different thickness on the structural and electrical properties were studied and optimized for use as gas sensor. The stability of the films against time and temperature variations was studied. The effect of the catalytic layers on the sensor microstructure and its performance towards the gas sensing application was observed. (C) 2005 Published by Elsevier B.V.