Nanocrystalline indium tin oxide films are deposited in a reactive oxygen atmosphere with background pressure at 0.02 mbar on glass substrate at different substrate temperatures (T-s) ranging from 300 to 573 K using pulsed laser deposition technique. The films are characterized using GIXRD, AFM and UV-visible spectroscopy to study the effect of substrate temperature on the structural and optical properties of films. The XRD patterns suggest that the films deposited at room temperature are amorphous in nature and the crystalline nature of the films increases with increase in substrate temperature. The thickness of the film decreases with increase in substrate temperature. The AFM data show that substrate temperature plays a dominant role on the surface morphology of the films. UV-visible spectra show that all the deposited ITO films exhibit a direct allowed transition. The higher value of optical band gap obtained for the films may be attributed to quantum confinement effect. The films deposited at higher substrate temperatures show higher value of transmittance. (c) 2007 Elsevier B.V. All rights reserved.