This report showcases international regulatory co-operation (IRC) in the areas of competition law and chemical safety. These two studies – covering very different subjects – are rare examples of areas where complex legal and institutional frameworks have been created at the domestic and/or international level to ensure effective IRC. The competition case study focuses on international co-operation for law enforcement, surveying the range of tools and methods countries can use to address international antitrust concerns, as well as the challenges involved. The chemical safety case study reviews the OECD Environment, Health and Safety Programme and provides concrete evidence of the monetary and health benefits of its “mutual acceptance of data” system related to chemical safety. These case studies are evidence of both the importance and the complexity of frameworks that enable IRC to help solve common problems across jurisdictions.