This major text by the author of Mass Communication Theory offers a comprehensive analysis of the growing field of assessment and evaluation of the performance of mass media. Across different societies, with varying media systems, there is evidence of increasing concern with the nature and quality of media output as well as about the independence and diversity of media systems. In this broad-ranging overview, Denis McQuail outlines the varying means of media performance assessment which have been attempted. He analyzes the central questions of what the `public interest' means in this context, which criteria are relevant for assessing media performance, how such values are established and how they can be reconciled with the economic, industrial and audience market contexts. Both encapsulating a major area of recent debate and research, and advancing it to a new level, this book will be essential reading for students of media and communication studies and for those actively involved with media policy and practice.