The optical properties of vapour chopped and nonchopped bismuth oxide thin films of two thicknesses 1500 A and 2000 A have been studied. The films were prepared by thermal oxidation in air; of vacuum evaporated vapour chopped and nonchopped bismuth thin films. As revealed by XRD studies, multiphase and polycrystalline bismuth oxide thin films were obtained. The refractive index was found to increase with the thickness and exposure to air for 40 days. The vapour chopped films showed higher refractive index, band gap and lower grain size than those of nonchopped films. The films showed high transmittance in the visible spectrum. The ageing effect on the vapour chopped films was found low. (c) 2007 Published by Elsevier B.V.