This paper examines the evolving ideological content of the concept of citizenship and particularly the challenges it faces as a consequence of the building of the European Union. From an epistemological point of view it is first argued that citizenship may be described as a dual concept: it is both a legal institution composed of the rights of the citizen as they are fixed at a certain moment of its history, and a normative ideal which embodies their political aspirations. As a result of this dual nature, citizenship is an essentially dynamicnotion, which is permanently evolving between a state of balance and change. The history of this concept in contemporary political thought shows that, from the end of the second World War it had raised a synthesis of democratic, liberal and socialist values on the one hand, and that it was historically and logically bound to the Nation-State on the other hand. This double synthesis now seems to be contested, as the themes of the "crisis of the Nation State" and"crisis of the Welfare state" do indicate. The last part of this paper grapples with recent theoretical proposals of new forms of european citizenship, and argues that the concept of citizenship could be renovated and take its challenges into consideration by insisting on the duties and the procedures it contains.