Spray pyrolysis system was used to obtain tin doped ZnO thin films on heated glass substrates. The structural, optical and electrical properties of the films were been studied. The effect of heat treatment for as deposited films in vacuum was studied. X-ray diffraction spectra showed that doping improves the crystallinity. Tin doped ZnO films with over 85% transmittance and conductivity as low as 5 x 10(-2) Omega CM were obtained. On the other hand, the annealing of as deposited films in vacuum leads to reduction of resistivity and improvement of crystallinity and optical transmission. (c) 2005 Elsevier B.V. All rights reserved.