EN
The aim of the present paper is to study the possibility of application of the X-ray quasi-forbidden reflection method to the composition determination of the sphalerite-type Cd_{1-x}M_{x}Te = Mg, Zn, Mn) single crystals. The method is based on the property of quasi-forbidden reflections that their integral intensity is very sensitive to composition and weakly sensitive to crystal lattice defects. An example of application for a Cd_{1-x}Mn_{x}Te single crystal is presented.