The book addresses the issue of product market integration within the European Union (EU) from a multidisciplinary approach that ranges from economics to political science and sociology. Besides the contributions from academia the book also includes the perspectives of the European Commission - Directorate Industry and Enterprise, and of the business community, thus providing a comprehensive overview of the issue under analysis. The book is organized around three main themes: plural perspectives and assessments of current market integration in the EU, empirical analysis of trade and trade barriers within the EU, and discussion of today's challenges in market integration. As such, the book starts by assessing the functioning of the EU Internal Market and by evaluating the need for differentiated integration in an enlarged and increasingly heterogeneous EU. It then proceeds with three empirical studies relating to intra-EU trade, focusing on technical barriers, on the importance of institutional factors in explaining non-tariff protection, and on the consequences of legal and administrative regulations on trade opportunities. The book ends by presenting and discussing today's challenges to market integration in a globalized world as well as the role of the EU in shaping a new mode of governance in transatlantic market integration. Regulation and governance in integrated markets are recurrent topics in the various chapters. The book presents state-of-the art academic research on product market integration and given its multidisciplinary approach it has distinguishing features that make it unique in the literature.