Most, if not all, countries have street gangs. There is considerable variety when it comes to their history, (criminal) activities and composition, but often migrant youth are among the members. These newcomers may find themselves in a marginal position, which can lead them to become gang-members. Apart from this socio-economic aspect, nowadays youth culture seems to promote a gang lifestyle and play a role in gang formation. This lifestyle is strongly influenced by stereotypical American gangs.The chapters in this book are based on research from twelve different countries. They address both situations where there have been longstanding problems with street gangs as well as areas where such issues have just started to emerge. Different research methods, both qualitative and quantitative, provide a unique insight into the influence of migration on local gang formation and development, paying particular attention to the importance of ethnicity. The chapters also explore the challenges that migration and ethnicity pose for responding effectively to the growth of such gangs, particularly in areas where public discourse on such issues is restricted. This peer-reviewed volume will be essential reading for anybody interested in the phenomenon of street gangs.This is the third book produced by the Eurogang network, consisting of researchers working together to develop a common framework for international comparative research on street gangs, based on standardised methodological instruments and a common research design. The Eurogang network started in 1998 and now has some 200 members working on various continents.