Some electrical and electroluminescent properties of evaporated ZnS and ZnSe films activated by manganese have been investigated. The electroluminescent brightness has been measured as a function of voltage and current for both a.c.and d.c. excitation. It is found that radiation is emitted throughout the volume of the film and that the intensity of this emission is determined both by the nature of the electrodes and the film composition. The results have been interpreted in terms of the acceleration-collision excitation mechanism, originally proposed by Piper and Williams. The possibility of an electron avalanche is considered since the electric field strength in the films is of the order of 10⁶ V cm^-1.No effects due to minority carrier injection were observed.