The objective of this paper is analysis of the changing socio-spatial situation of immigrants in the Lisbon Metropolitan Area during the 1990s. The theoretical framing of this analysis is built on several bases: the metropolitan area's particular urban history and planning processes; the post-industrial features which are common to Southern European cities; the nature of the welfare system; and the specific characteristics of the Lisbon housing market. The analysis explores the links between the circumstances of different immigrant groups and contemporary urban social processes, such as polarisation, exclusion, residential segregation, and fragmentation of the urban social fabric. Regarding differential effects and processes across immigrant groups, two dimensions of comparison can be stressed: the distinction between the labour immigrants, mainly from Portuguese-speaking African countries, and highly-qualified migrants from the European Union; and a further distinction between the 'first wave' of labour migrants from Africa, whose numbers grew sharply after the decolonisation process of the mid-1970s, and whose migration still continues, and a 'second wave' made up mainly of East Europeans, Brazilians and some Asian groups, who arrived after 1999-2000.