This book is an extensive review of the current state of illegal immigration in Europe and North America whilst providing theoretical analysis. This analysis models illegal immigration in a two-country framework, highlights the inter-related labour markets and considers a range of immigration policy instruments, including border patrols and employer surveillance and sanctions. Distinguishing between scenarios with and without the international mobility of capital, this book also examines various profit sharing arrangements. Other issues explored include: - The effectiveness of tighter border patrols and internal surveillance upon the level of illegal immigration - The effects upon national and international welfare - And optimal immigration policy choices