It is a common pattern across the world that immigrant groups are confronted with a mismatch between the language varieties of their source and target countries. During the twentieth century, the USA has been a target country for many European immigrants, whereas industrialised European countries have been the target area for many Third World immigrants during the past decades. As a consequence of socio-economically or politically determined processes of immigration, the traditional patterns of language variation across Europe have been considerably extended over these decades. Many industrialised European countries show evidence of a growing number of immigrant populations which differ widely, both from a cultural and a linguistic point of view, from the mainstream indigenous population. It has been estimated that in the year 2000, one third of the population under the age of 35 in urban Europe will have an immigrant background. The focus of this volume is on immigrant groups and immigrant languages with a recent or earlier background of migration to industrialised countries in Western and Northern Europe. The book is divided into four parts. Part 1 gives a general overview of immigrant language varieties in Europe. The focus of Part 2 is on processes of first language acquisition in a second language environment. Part 3 deals with the study of codeswitching, and Part 4 with the study of language maintenance and language loss. In order to allow for crosslinguistic comparisons, different immigrant language varieties in various European countries are taken into account in all four Parts.