Immigration, and in particular illegal immigration, is among the top international social, economic and security policy concerns of our time. Globalization has created a widening asymmetry: capital, information and goods are free to flow across borders whereas labour mobility is subject to many restrictions. This creates a tension between institutional goals, market forces and individual aspirations and as a consequence migration is increasingly driven underground. This book discusses the history of the idea of 'illegal immigration' and its political economy. In four case studies, it analyses the motives and strategies of undocumented immigrants in Europe, revealing typical risk biographies. In assessing European migration policies it concludes that a no-win conflict is generated, with negative effects on all sides. It offers an assessment of contemporary political responses, and proposes an alternative approach which aims to provide a more sustainable solution.