Since most research on economic metropolisation has until now concentrated on "high added value" workers on both sides of the border, little place is left for analysis either of the less valued categories in the process of metropolisation, or of the diversity of jobs within the regional labour markets. What, then, is the position of less favoured social categories in the evolution of cross-border metropolises over the last decades, when compared with managers or other liberal professions? To answer this question, a case study is carried out here on the cross-border commuters in the Lorraine Region (France), who participate in great numbers in the metropolisation of Luxembourg, by comparing them to those who work in France. The objective of this article is to give an account of the spatiotemporal evolution of the principal social classes among the cross-border commuters, based on the French population censuses. These databases, from 1968 to the present day, are comparable both in the time and space. The results confirm that a cross-border metropolis of Luxembourg has been formed, notably since the 1990s, by a substantial increase of highly qualified cross-border commuters, as well as by an augmentation of the less qualified workforce during this period: thus, in the Region of Lorraine, even in 2013, the share of the cross-border working class (commuting to Luxembourg) remains greater than that of the working class within France. Moreover, complex links exist in the phenomenon of metropolisation between historical social segregations and specifically metropolitan segregations in terms of the socio-spatial organisation of the territory in question: for example, the secondary urban centres of the French metropolitan area, such as Thionville or Metz, serve as a residential reservoir for the most highly qualified cross-border commuters, especially when this type of workforce has already been observed in these agglomerations in the past. Primary results point to the need to learn more about the conditions of different ...