${\mathrm{Cd}}_{\text{1−x}}{\mathrm{Zn}}_x\mathrm{Te}$ thin films were prepared on 7059 Corning glass substrates using an rf magnetron sputtering system and $\mathrm{CdTe}\text{(1−y)+}\mathrm{ZnTe}\mathrm{(y)}$ targets. The concentration (x) of Zn in the films did not coincide with the relative weight (y) of the ZnTe powder in the compressed targets. Values of x were in the range 0–0.30 as determined from x-ray diffraction patterns. The band gap energy ${\mathrm{(E}}_g)$ of the ${\mathrm{Cd}}_{\text{1−x}}{\mathrm{Zn}}_x\mathrm{Te}$ samples was calculated from the photoreflectance spectra measured on the films. The position of the experimental points in the $E_g$ versus x plot show a deviation from the phenomenological quadratic relation $E_g{\mathrm{=E}}_{\text{g0}}{\mathrm{+ax+bx}}^2$ calculated within the virtual crystal approximation (VCA). The depart of the $E_g$ values for higher Zn concentrations from the expected VCA model is probably due to a larger clustering of Zn atoms and/or a percolation phenomena. We obtain fitted values for the parameters a and b within the VCA approach. Comparison with data reported by other authors is made.