In2O3 thin films have been deposited on glass substrates by spray pyrolysis. InCl4 was used as the solute to prepare the starting solution with a concentration of 0.1 M. The films were grown at different substrate temperatures ranging from 300 to 400 degrees C. The as-grown layers were optically characterized in order to evaluate the absorption coefficient, optical band gap, refractive index, extinction coefficient and other optical parameters. The influence of substrate temperature on these parameters was reported and discussed. (c) 2006 Elsevier B.V. All rights reserved.