This project has dealt with the question why the European market for asset management and investment funds is still characterised by a large relevance of national borders. The empirical work was based on two sources: First, an extensive collection of aggregate data on the European fund market with a focus on cross-border business and, second, the results of a number of interviews with leading UK based investment companies. According to these insights, incomplete integration can be tracked down to the following factors: tax reasons are the most important single obstacle for difficulties in cross-border-business. A specific problem results from national legislation concerning cross-border mergers of funds. The relevant legislation often poses a substantial burden on these mergers. Further problems are related to the fields of registration, consumer protection, distribution and infrastructure. The study’s insights could be condensed into specific conclusions for shaping future integration politics. An example concerns the present registration obligations for each single national market. These obligations should be given up once a fund is registered in one EU country.