This book addresses the meanings and implications of multilingualism and its uses in a context of rapid changes, in Europe and around the world. All types of organisations, including the political institutions of the European Union, universities and private-sector companies must rise to the many challenges posed by operating in a multilingual environment. This requires them, in particular, to make the best use of speakers’ very diverse linguistic repertoires. The contributions in this volume, which stem from the DYLAN research project financed by the European Commission as part of its Sixth Framework Programme, examine at close range how these repertoires develop, how they change and how actors adapt skilfully the use of their repertoires to different objectives and conditions. These different strategies are also examined in terms of their capacity to ensure efficient and fair communication in a multilingual Europe. Careful observation of actors’ multilingual practices reveals finely tuned communicational strategies drawing on a wide range of different languages, including national languages, minority languages and lingue franche. Understanding these practices, their meaning and their implications, helps to show in what way and under what conditions they are not merely a response to a problem, but an asset for political institutions, universities and business.