Amorphous Ge{sub x} Se{sub 9}0-x Sb{sub 1}0 thin films prepared by thermal evaporation onto glass substrates. Reflectance and transmittance were measured in the wavelength range 190-900 nm. The optical properties of the as deposited and UV-irradiated films at different exposure times were reported. The compositional-dependence of the optical constants (absorption coefficient, the non-direct optical gap E{sub g}, refractive index (n)) were evaluated and discussed in terms of the Ge content.