The presence of migrant workers has become a central feature of labour markets in highly developed countries. The International Labour Organisation estimates that in 2013 there were 112 million resident migrant workers in the 58 highest-income countries, who made up 16% of the workforce. Non-resident workers have also increasingly become part of the labour available for employment in other states, often on a temporary basis. This work takes a thematic and comparative approach to examine the profound implications of contemporary labour migration for employment law regimes in highly developed countries. In so doing, it aims to promote greater recognition of labour migration-related questions, and of the interests of migrant workers, within employment law scholarship. The work comprises original analyses by leading scholars of migration and employment law at the European Union level, and in Australia, Canada, Germany, Italy, the Netherlands, Spain, the United Kingdom and the United States. The specific position of migrant workers is addressed, for example as regards equality of treatment, or the position in employment law of migrant workers without a right to work. The work also explores the effects of migration levels and patterns upon general employment law - including the law relating to collective bargaining, and remedies against exploitation.