Regulatory impact assessment (RIA) is the main instrument used by governments and regulators to appraise the likely effects of their policy proposals. This pioneering Handbook provides a comparative and comprehensive account of this tool, situating it in the relevant theoretical traditions and scrutinizing its use across countries, policy sectors and policy instruments. Comprising six parts, university researchers, international consultants and practitioners working in international organizations examine regulatory impact assessment from many perspectives, which include: • research traditions in the social sciences • implementation, regulatory indicators and effects • tools and dimensions such as courts and gender • sectoral case studies including environment, enterprise and international development • international diffusion in the European Union (EU), Americas, Asia and developing countries • appraisal, training and education. With its wealth of detail and lessons to be learned, the Handbook of Regulatory Impact Assessment will undoubtedly be of great value to practitioners and scholars working in governance, political science and socio-legal studies.