A state of the art review of discomfort glare in the interior working environment is given, and a CIE mathematical model, or system, is proposed for the prediction of discomfort glare from lighting installations. The first part of the report contains a review of basic principles and methods of glare control and glare prediction systems used in various countries. The second part contains a critical review of research and major current prediction systems. This leads to the proposed CIE system, which incorporates current knowledge insofar as possible. While this report is not intended to be the final statement on the subject, there has been considerable research to warrant its publication by the CIE. The report will assist countries in revising established systems, and other countries in adopting a particular system. It will also assist lighting students, as well as architects, consultants, and others associated with lighting, in understanding the phenomenon of discomfort and glare and its control.