Cathodoluminescence in hexagonal zinc sulphide single crystals has been investigated by irradiation of specimens at 100 °K with 30 keV electrons in a scanning electron microscope. The effects on the luminescence of stacking faults have been observed by simultaneously recording both the luminescence micrograph and the emission spectrum, and by subsequent examination of the same single crystals in a transmission electron microscope. With thicker crystals, opaque to the latter, an intense emission was observed from thin basal plane intergrowths, which was strongly dependent on the electron current density.