Crystal face temperatures of single crystals of &agr;‐HgI2growing in transparent ampules by physical vapor transport have been measured,insitu, by a novel, noncontact method which may be called reflectance spectroscopy thermometry. The method is based on the temperature dependence of the energy of the free‐exciton peak as detected with a low‐energy reflected beam. As presently configured, the accuracy is ±1.5 °C for a slowly varying surface temperature. The method has potential for noncontact temperature measurement in some systems for which pyrometry is unsatisfactory.