In all countries of the European Union, the Muslim communities, numbering about 15,000,000 people, represent a substantial religious minority, although it is a very varied group, both in terms of religious practice and national origin. The very weight of this minority forces the legal systems to come to terms with its presence. However, these changes are highly diversified and are evolving rapidly, not necessarily towards greater tolerance. This volume provides a brief sketch of these changes, describing the situation of some member countries of the European Union (Austria, Belgium, France, Germany, Greece, Italy, the Netherlands, Portugal, Spain, Sweden and UK) and of one of the enlargement candidate countries, Romania. The book also contains an initial attempt at comparison between European countries and the USA and an overall analysis of the problems posed by the Islamic presence in Europe and the strategies to manage them. This work allows readers to draw some general conclusions on convergences and divergences within the European Union and the factors that determine them.