The process of formation of the Romance languages from the end of the ancient world to the age of Charlemagne has fundamental sociolinguistic implications, regardless of the preferred line of theoretical explanation. The Romance vernacular side is less easy to investigate, and here it is evident that diatopic variation was accompanied by typically sociolinguistic differences of status. In the Romance world there are few remaining cases of a degree of socio-cultural homogeneity so great that there is no need for some diastratic variation. The interplay of sociolinguistic relations between Romance and non-Romance varieties, which the authors have occasionally alluded to, is no less varied and wide-ranging than what happens within Romance. This chapter mentions two aspects: the historical side, which implies shifts in the external linguistic boundaries of the Romance linguistic family and the coexistence, particularly in modern times, of different types of language in the same area.