This chapter begins with a brief introduction highlighting two key recent works selected for their understanding of historical and comparative dimensions in the evolution of quality assurance. It goes on to outline the range of methodological approaches from critical analysis and empirical research at the national level, to smaller scale qualitative case studies of the impact of inspection locally, and on to international comparative studies. Following consideration of the cultural and political contexts of inspection, a representative selection of studies is then reviewed under headings defined by research focus and methodology: national policy and theoretical critique; empirical studies of national practice; case studies of local experience with particular regard to teachers; teachers, curriculum and emergent self-evaluation; and comparative international studies. Key findings and insights from the research are synthesised, implications for current policy and practice are considered, and suggestions for further research are made.