Drawing on a range of case studies, this systematic study demonstrates the variety of language usage in seventeenth-century France, a time considered to be the most "standardizing" in the history of French. Variation is analyzed in terms of gender, age and socio-economic status, or by the medium, register or genre used. The case studies present phonological, morphological, syntactic and lexical issues, posing a range of methodological questions for sociolinguists and historical linguists.