The infrared absorption spectra for a sample of Hg1−xCdxTe withx= 0·19 reported previously have been recalculated including both the absorption due to individual carrier transition and that due to collective excitation of carriers (plasmons), taking into account the dispersion of refractive index and the non-parabolicity of the energy band in the absence of Landau damping. The agreement between theory and experiment is good and suggests that free-carrier absorption due to collective excitation can play a noticeable role in the frequency range from ωpup to 2ωpand above. The value of the concentration of ionized impurities thus obtained is believed to be more accurate than that obtained previously.