Over the last 20 years there has been a vigorous discussion of evidence related to new and more intense social and spatial divisions within European cities. These contributions have identified social and spatial polarization associated with globalization, deindustrialization and the increasing income inequalities arising from these. However, various ‘moderating’ factors were identified to explain why different outcomes were emerging in European cities than in their American counterparts. In this context much of the literature has focused on types of national welfare state and as these arrangements have come under pressure across Europe it may be expected that differences from the USA may decline. However there are other literatures that, rather than emphasizing the importance of national welfare states, refer to the stronger interventionist traditions of European governments and the distinctive characteristics of European cities. Differences in these dimensions within Europe– including those related to urban planning and recommodified housing– do not correlate with typologies of national welfare states and suggest continuing divergence within Europe and between Europe and the USA. Working within this framework, this introduction to a special issue argues that although European welfare states have weakened, other factors continue to sustain differences between European and American cities. When looking at newly emerging spatial patterns, the major economic and political changes experienced in countries in Central and Eastern Europe are important in explaining why these countries often show causes and effects that differ from their counterparts in Western Europe. Research into spatial segregation is not new. The works of many researchers working within the Chicago School are known to all geographers. These human ecologists can be seen as the first group of researchers who systematically paid attention to the description of patterns of spatial segregation (see e.g. Burgess 1925; McKenzie 1925). At the time this work was carried out, it was usual to regard the city as a separate entity: the wider world almost seemed not to exist and certainly not in the form of globalization and international. Their field of study was Chicago and they described segregation as consisting of concentric zones (Burgess 1925), sectoral patterns (Hoyt 1939) or multiple nuclei (Harris&Ullman1945).The zones, sectors and nuclei housed different parts of the population, and this is indeed the central issue of segregation.