Since the 1950s, in many parts of the world, labour migration movements have been facilitated – to a lesser or greater extent – among selected groups of countries, generally characterised by close geographical proximity and historic and economic ties. Such liberalisation of international labour mobility has generally developed in the context of a broader process of regional economic integration, and has tended to be introduced in the latter phases of this process. The degree to which labour migration is facilitated varies with the level of regional integration. Only in a limited number of cases has the liberalisation of international labour mobility in the context of regional economic integration processes led to the establishment of free labour mobility areas, involving full and equal labour market access for all member countries’ nationals. The great majority of such free-movement areas are to be found among OECD countries.