The influence of the choice of wavelength on the resolution of silicon wafer temperature measurement by ellipsometry has been investigated. By changing the wavelength from 6328 to 4428 angstrom, a 30% reduction was achieved in the rms difference between the temperature measured by ellipsometry and that measured by a thermocouple. Additional optical data are presented which provide insight into selecting the optimum wavelength for silicon wafer temperature measurement by ellipsometry.