Polarization has been observed and measured for the banded luminescence emission in single crystals of cadmium sulphide in the wavelength range 1 5-2 2 μm and for the corresponding excitation spectrum. The experimental results lead to an energy level model for the infra-red emission centre in which the complexity of the emission is explained by considering the lifting of degeneracy (by spin-orbit splitting and crystal field splitting) in both the upper valence band and the localized acceptor level which is the excited state of the centre. Polarization of the 1 06 μm emission band can be explained on the same model.