Evidence exists that, in the past, phonetic variants functioned as sociolinguistic variables, just as they do today, at least in societies with comparable stratificational patterns. This paper presents the significant details of the sociolinguistic environment within which the beginnings of the Great English Vowel Shift were embedded. An attempt is made to demonstrate how an understanding of the sociolinguistic situation surrounding historic changes leads to an understanding of the transition from earlier to later pronunciations. It is demonstrated that: (1) contemporaneous changes in the social and linguistic profiles of England during the 14th century led to a situation in which two regional dialects were juxtaposed and realigned as social dialects; and (2) the different phonological histories of the convergent dialects provided the raw material for sociolinguistic variation at that particular time, when older sociolinguistic barriers were disintegrating in England. It is hypothesized that the type of cross-dialectal phonological restructuring that has been observed in contemporary settings would have led to the initial phase of the Great Vowel Shift as a matter of course, given the phonetic variation and socio-dialectal alignment pattern that have been reconstructed for Early Fifteenth Century London English. (CLK)