Following the introduction of the euro, the European Union has started to debate the desirability and feasibility of more co-ordination in the field of capital income taxation. In contrast with product taxes, the EU Treaty does not provide for explicit authority to harmonize income taxes. So far, little co-ordination has taken place, even though the capital income tax base is much more mobile and hence more difficult to tax than consumption. The papers in this volume attempt to foster discussion on whether, where, and how capital income should be taxed.