An Analysis of Transborder Cooperation Structures inWestern Europe within the Context of European Integration and Decentralisation Towards Regional and Local Governments. Aygen Aykaç is a Ph.D. student of transborder cooperation in Western Europe at the London School of Economics and Political Science. She has worked at the transborder cooperation unit ofthe Directorate-General for Regional Policies of the European Commission. Aykaç iscurrently a parliamentary assistant at the European Parliament and is set to join the staff of the Council of Europe as an administrator. "Transborder Cooperation Structures" (TBSs) mentioned in Aykac's paper refer to the institutions or working arrangements established by municipal/provincial/regional/national authorities in border areas involving two or more countries in order to solve common problems and to enhance economic development. "Transborder Regionalisation", on the other hand, refers to the process of establishing and strengthening such institutions. It is based on the assumption that the cross-border area isan economically, geographically and/or culturally homogeneous entity like a national "region", and that this gives the legitimate basis for establishing common institutions. The TBSs are not a new phenomenon, yet new ones are being formed and the old ones are being reformed to adapt to new requirements. Their evolution is influenced on one hand by the decentralisation policies of national governments and on the other by the process of European integration. The EUREGIO, which involves one German and two Dutch municipal associations, was initiated in 1958 and subsequently has been reformed several times. Some other examples of the TBSs at the subnational level are the Dutch-German MAAS-RHEIN (1976), EMS-DOLLART (1977) and RHEIN WAAL (1978); the French-German CIMAB (1964); the SpanishFrench Working Community of the Pyrenees (1983); and the French-Italian-Swiss COTRAO (1982). At the national level there are the regional planning commissions, such as the BENELUX and German-Dutch Regional Planning Commissions or other intergovernmental commissions such as the SAR-LOR-LUX and the FrenchGerman-Swiss Commissions which, like the Euregios and Working Communities, have working groups on various fields such as tourism, culture, transport, education, economy, social issues and regional planning. Although TBSs such as the EUREGIO, the planning commissions mentioned above and the European Development Pole are examined in detail, the aim of Aykaç's paper is not so much to give an extensive account of each of the TBSs. The paper touches upon the cultural, politico-administrative, legal and economic factors which influence the evolution of transborder cooperation and its institutionalisation. This helps to form the basis of looking at the TBSs from a new angle. What is their role in a centre-periphery perspective and where do they fit, in the regionalisation and decentralisation theories and policies? Could they help us understand the relationship between European integration and decentralisation? While trying to find answers to such questions, the paper introduces fresh approaches to old concepts and explores the potential role of the EUREGIOs in the reshaping of the new territorial map of Europe.