Thin films of copper indium diselenide (CuInSe2) were prepared by selenization of CuInSe2-Cu-In multilayered structure on glass substrate. The selenization procedure was carried out in a vapour of elemental selenium in a vacuum chamber. The obtained films were characterised by XRD and SEM measurements. The effects of substrate temperature on the structural, electrical and optical properties were studied. It was found that single phase CuInSe2 thin films with significant adhesion to substrate can be produced by selenization of CuInSe2-Cu-In multilayered structure at 450 degrees C, when the first non single phase CuInSe2 layer was deposited at substrate temperature of 400 degrees C. The thin films were found to be direct band gap semiconductors with a band gap of 0.97 eV. (C) 1999 Kluwer Academic Publishers.