Islam has become the key site for demarcating boundaries between majority populations and individuals of immigrant origin across Europe. This article outlines a research agenda on the socio-cultural integration of Muslims in their Western European societies of settlement. Integration issues with regard to Muslims have especially tended to focus on cultural and religious aspects. This raises questions. First, does culture/religion matter in shaping Muslims’ relative disadvantage in the socio-economic domain? Alternatively, does Muslim social disadvantage result from majority society's discrimination and bias against religious/cultural difference?

Second, religious and cultural difference seems to matter in its own right. Do Muslims identify with their countries of settlement and accept the core liberal democratic values and norms? Or do persistent socio-cultural ‘gaps’ between Muslims and non-Muslims result from intolerance by the majority population? The article outlines a theoretical approach and empirical research programme.

The framework is cross-national comparative, including France, Germany, Britain, Netherlands, Belgium, and Switzerland. The main data source is a survey that includes four groups of Muslims from distinct countries of origin (Turks, Moroccans, former-Yugoslavians, and Pakistanis) plus a majority sample, which facilitates cross-group, cross-national comparison. This introduction concludes by introducing contributions that address a specific question embedded within the overall framework.