A method for the fabrication of p-n junctions in zinc sulfide was developed. The current-voltage characteristics, phto-emf, and electroluminescence of these Junctions were investigated. The results obtained were used to estimate the barrier height, donor level depth, and forbidden band width of ZnS single crystals. The mechanism of current flow through a p-n junction was analyzed. Information on the electron energy states and the mechanism of electroluminescence was obtained from the electroluminescence characteristic. A comparison was made between the characteristics of p-n junctions in zinc sulfide and those of ZnS:CuzS heterojunctions. This comparison was used to obtained more information on the mechanism of the electro luminescence of ZnS single crystalS.