In the course of the last two decades the number of arrests, imprisonments and detention of aliens and citizens of foreign origin, has gone up considerably in all European countries, both of old and new immigration, as well as in North America, Australia, Japan and recently even in countries that function as emigration and transit countries. This phenomenon has attracted the interest, not only of criminologists, but also of scholars from other social sciences. The aim of our work is to bring together some of the most qualified and experienced scholars in this field, in order to make an appraisal of the state of knowledge existing in this area and suggest avenues for further research.