The author analyzes, from a historical sociolinguistic point of view, selected domains of morphosyntactic variation in a 250,000 word collection of the Middle English Paston Letters (1421-1503). In three case studies, two nominal and one verbal variable are described and discussed in detail: the replacement of Old English pronouns by borrowed pronouns, the introduction and spread of >wh-relativizers, and the spread and routinization of light verb constructions (take, make, give, have, do plus deverbal noun).