Polycrystalline CdSx,Te1-x thin films, grown on glass substrates by co-evaporation of CdS and CdTe were characterized through spectral transmittance and x-ray diffraction measurements. The film thickness d and the optical constants were determined by simple straightforward calculations using the transmission spectrum alone. From x-ray diffraction measurements and data of the chemical composition obtained from x-ray fluorescence measurements, is shown that thin films of CdSxTe1-x mixed crystals with any composition can be obtained by this method.