The basic experimental results found in studies of the emission of thin single-crystal layers of rock salt in superhigh electric fields are classified and analyzed. The emission is shown to come from the salt layer and to be due to electronic processes in this dielectric. The basic characteristics of the emission are analyzed, and it is shown to be electroluminescence. The estimated concentration of luminescence centers, data from chemical analysis, and the independence of the spectral characteristics from the “past history” of the samples indicate that the luminescence centers are due to defects in the crystal matrix.