This paper aims to support better-targeted and more homogeneous data collection and comparative analysis of regulatory oversight bodies (ROBs). To do so, it builds on relevant academic literature and available data to sharpen the definition of ROB used in OECD analytical work and policy discussions. It also discusses ROBs’ role within the regulatory governance cycle, as well as various aspects related to regulatory oversight and co-ordination, with special attention to the overall institutional setting (including the relationships between various ROBs), context and objectives of regulatory reform, tasks and responsibilities, and associated accountability arrangements.