The analysis of classroom observation data is seen as increasingly important in research on the impact of high-stakes language tests or new foreign-language programmes on students, teachers and other stakeholders. Video-recordings of language teaching and learning in classrooms impacted by such tests or programmes can provide revealing data, which, however, may be difficult to analyse in raw recorded form. The organisation of video-recordings into an interactive database facilitates the retrieval and analysis of data in response to particular research questions. Informed by current research on the use of video in education, especially educational research, and by the relevant video database literature, this paper describes a video database developed by the University of Cambridge English for Speakers of Other Languages (Cambridge ESOL) Examinations operation, part of Cambridge Assessment, the new identity of the University of Cambridge Local Examinations Syndicate (UCLES). This paper describes three Cambridge ESOL impact studies for which the data were collected, and discusses the video-recording equipment used, approaches adopted and decisions made. It then outlines the aims, principles and approaches involved in the development of the impact research video database, including software selection, main design features and envisaged future uses. A step-by-step account for the likely video database user is included, along with sample screenshots. (Contains 3 figures.)