T h e paper presents a critical account of electroluminescence, with particular reference to the work of the last few years on such aspects as spectral characteristics, intraband relaxation, trapping processes, participation of crystal surfaces, contact phenomena, photo-electroluminescence and field enhancement processes. Recent experiments on injection (including tunnel injection) electroluminescence in zinc sulphide and intermetallic compounds are given special emphasis and their relevance to the traditional problems associated with phosphor materials is considered in some detail. There is also an introductory outline of the closely related junction laser phenomena. The paper is intended, both as a discussion of the issues which are now in need of further clarification, and as a retrospective review of 'source' material.