Abstract
How important is ethnicity for group formation in immigrant societies? Multiculturalism and the racialization (or ethnicization) hypothesis give opposing answers to this question. This article provides an empirical contribution to the debate by looking at patterns of group formation on the level of social categories and personal networks in the immigrant neighbourhoods of Basel, Bern and Zürich. We find that ethno-national categories are secondary principles of classification only but that the social networks are ethnically largely homogeneous even in the second generation. We conclude by advocating the use of more differentiated analytical tools to explain this variability of patterns.