Although cross-border cooperation is often thought of as involving adjacent regions, transnational cooperation is increasingly important, particularly within the European Union and among its European neighbours. Transnational cooperation often involves networks of several participating regions, at a variety of levels: local governments (NUTS 4 and 5 regions), regional governments (NUTS 3) and supra-regional governments (NUTS 2). Looking at NUTS 3 regions in five countries, this paper examines different forms of transnational cooperation and examines their success. Exchange of best practice, networking, learning about the experience of other regions in a similar situation, learning about mistakes to avoid and greater clout in European decision-making are all reasons for transnational cooperation. In some cases, they have started as a way of delivering aid, in the form of goods or training, or sharing experience with new EU member states. However, most of these have evolved into mutual exchanges, offering both sides a chance to learn from each other and share experiences. Some have a narrow focus and are organised in the form of discrete projects with a limited term. Others take the form of ongoing collaboration across a range of fields. As well being mediated through the European Union, some partnerships operate through other European networks, particularly the Assembly of European Regions (AER), the Conference of Peripheral Maritime Regions of Europe (CPMR) and the Association of European Border Regions (AEBR). Often, transnational partnerships were originally created by local authorities which were later subsumed into larger regions. These regions have in turn adapted and extended the agreements. Not all partnerships are within Europe: one region has links with Guangdong Province in China, aimed at promoting the development of herbal medicine. Regional propinquity is not a requirement for successful cooperation. Success depends more on the focus of the programme and how projects are defined. Successful cooperation often requires a champion or set of champions to push forward cooperation and engagement. They work better if regional authorities have some control over finance and over policy-making.