In a globalized world the taxation of employees who spread their activity - and thus their income - across several countries is of particular importance. However, practical experience shows that the taxation of such "migrant birds" is subject to various difficulties. Issues are caused on the one hand by the interpretation and application of the relevant distributive rules in tax treaties and their independence with other treaty provisions which may lead to double taxation or double non-taxation and on the other hand by the fact that crossborder employees are often confronted with discrimination, both in their state of residence and in the respective source states. The master theses contained in this volume analyse these issues form the prespective of Tax Treaty Law as well as European Community Law and strive to develop solutions.