This volume, which comprises a collection of papers by leading Soviet researchers, is devoted to topics in the luminescence of semiconductors. An experimental check is made on a series of predictions of the theory of ionization domains. A new low-voltage luminescence of zinc sulfide is described and investigated and is found to be due to a high-frequency electrical instability. A detailed study of the electrical properties of the instability and of the characteristics of the emission testifies to the pre-breakdown character of the electroluminescence and to the acousto­ electrical nature of the instability. The luminescence excitation spectra of AIN crystals excited in the region of the fundamental absorption contain lines belonging to excitons and their phonon replicas. The symmetry of the electronic and vibrational transitions corresponding to parts of these lines is interpreted. The results of a study of the scattering of light by electron - hole drops in germanium are cited. The results are discussed on the basis of a theory of exciton condensation in which allowance is made for the diffusion of excitons toward the surface of the drops and for the surface tens ion of the electron - hole liquid. This volume will be of interest to a wide range of scientific workers, particularly those engaged in the study of luminescence and physics of semiconductors.