It is a long-established commonplace in any debate on immigration that immigrants should integrate into their receiving society. But integrate into what precisely? Into the labor market, into the legal order, into the political system, into a national culture whatever this might comprise? The Article tries to approach the question from the legal point of view and looks for hints or clues in the constitution which might help us with the answer. For this purpose, it explores the general theory of the constitution as it has been shaped by its professional interpreters as well as by political actors, the media and the public. The main intuition is that “constitution” is not only a written document, a text with a predefined, though maybe hidden meaning; instead, it is a social practice evolving over time and thereby reflecting the shared convictions of a political community of what is just and right. Talking about constitutional expectations toward immigrants then also tells us something about ourselves: about who we are and what kind of community we want to live in. As it turns out, we may not have a very clear idea of that.