Tin oxide (SnO2) thin films were prepared by a simple and inexpensive spray pyrolysis technique from an aqueous solution at various substrate temperatures viz. 300, 400 and 500 degrees C, and their electrochemical studies have been carried out. The thin films have been optically and electrochemically characterized by means of transmittance, cyclic voltammetry and chronoamperometry. The mechanism of reduction and oxidation reactions that took place during the potential cycling is presented. The samples deposited at 500 degrees C exhibit better performance in terms of coloration efficiency, reversibility, contrast ratio and response time. (C) 2007 Published by Elsevier B.V.