Phonological and morphological variation in Classical Latin (e.g., diphthongs ae/au vs. monophthongs e/o, retention vs. loss of final consonants and initial h-, GEN SG -is vs. -us/-os, DAT SG in -ae vs. -a, etc.) has typically been treated as regional in nature. However, these seemingly “rural” features cannot be considered instances of purely geographically based variation, for they also occur both on inscriptions from within Rome and in Roman literary usage. Coleman (1990:14) hinted at “a social dimension” to this variation, but only for au versus o variation. We argue, however, that a distinctly social dimension must be recognized for much of this variation, based on: (a) instances of hypercorrection; (b) the observation that datives in -a occur only in private, primarily domestic, inscriptions and never in public or official inscriptions; (c) Augustus's use of “rural” domos for domus, in keeping with the populist image he cultivated upon his return to Rome. This dialectal/sociolectal situation can be best understood, we argue, in terms of the model of urbanization of Milroy (1980) and Bortoni-Ricardo (1985). The transformation of originally geographic variation into socially determined variation in an urban setting resulted from migrations into Rome and the expansion of Rome after the 4th century b.c.