The spectral emission distribution of the luminescence at 77°K of cadmium sulphide crystals excited by ultra-violet radiation (λ = 0.365 μm) has been examined. The structure of the edge emission spectra obtained depends on the manner in which the crystals are prepared. `Pure' crystals are compared with samples grown in the presence of oxygen, chlorine, iodine or indium. The results indicate that in many samples the emission spectrum is a superposition of two separate spectra, associated with two distinct recombination routes. The results are interpreted to indicate that sulphur vacancies introduce an energy level 0.14 eV from a band edge, and sulphur interstitials a level at 0.17 eV. Substitutional indium gives rise to a level 0.15 eV from a band edge.The spectrum of the recombination radiation emitted at 77°K when electrically injected electrons and holes recombine has also been examined.