Abstract: An ellipsometric procedure developed for noncontact in situ measurement of the CdTe buffer-layer temperature is presented. The procedure is based on the temperature dependence of the energy position of CdTe critical points and is intended for determining the initial temperature of the growth surface before epitaxy of the cadmium–mercury–telluride compound. An express method for determining the position of critical points by the spectra of ellipsometric parameter Ψ is proposed. A series of calibrated experiments is performed. They result in determination of the temperature dependences of the position of critical points. Estimations and the experiment show that the temperature-measurement accuracy is ±3°C.