The social composition of immigration in France shows a plurality of “ethnic groups”, communities, professions and religions. Regarding Sub-Saharans and North Africans, differentiation begins with the phenotype, and then becomes prejudices in social relation between individuals and groups. The life of North African and Sub-Saharan immigrants in foyers (hostels used for their accommodation) since the 1950s, as well as later in urban neighbourhoods, is characterized by a grouping which has reinforced ethnicization. Both populations occupy spaces according to their origins and cultures. Moreover, “racialization” on the basis of skin colour may have created a gap between the Sub-Saharan population and the North African population which is wrongly considered as a homogeneous “immigrant” group.What kind of relationship exists between the Sub-Saharan populations and the North African populations in France? What kind of sociability exists between Sub-Saharans and North Africans of the same generation? Have social barriers made relationships particularly sensitive on the issue of matrimonial alliances and the ensuing kinship relationships? Have both North Africans and Sub-Saharans succeeded in adapting their lifestyle with that of their host society's distinct traditions? What is the consistency of the notion of fraternity between Sub-Saharans and North Africans? By whom and how is it expressed? Other than a confessional (Islamic) fraternity, is not there evidence of the erosion, the questioning, or even the disappearance of a form of solidarity and fraternity? Finally, how do the transformations that take place in concrete living conditions (work, housing) influence sociability, and more generally the relationship with others?My study focuses on the relationships between the groups of “Afro-Maghreb immigrants of France” within the social reality of daily exchanges. The “slave cleavage” and its representations associated with (black) skin colour may have created a gap in social life between the Maghreb group and the Sub-Saharan group. Their effect is felt in every society where both groups live together. This social disqualification may have affected matrimonial ties. The reasons are often related to black (and white) disqualification, which revives the memory of slavery for Blacks among Arabs, which explains why Arabness is associated with negative representations among many Sub-Saharians today. The thesis is divided into five parts, the first part outlines the purpose of this research and its narrative, which are followed by the lexicon of “racializing” that Afro-Maghreb relations have generated over time. This section also provides an overview of the populations we study, the areas where they live, as well as the methods used during this research. In the second part, we have defined “groups and their borders”, North Africans and Sub-Saharans across space and through human history. Then, we discussed the criteria of morality and assessment factors for the Afro-Maghreb community. In this section, we have given more importance to mobility and interaction, first in the context of relations between the Maghreb and Sub-Saharan Africa through history, particularly the pre-colonial period. Then we have addressed Afro-Maghreb immigration and post-colonial interethnic cohabitation up to the present day.