This article examines grammatical conditioning of the use of nonstandard -s in expletive there sentences. The discussion is based on data from a Midlands variety of English (UK). In negative constructions, speakers tend to allow for nonstandard -s with no and constituent not, but not to use it with n't or clausal not. Further, nonstandard -s is admitted in declarative existentials, but disfavoured in interrogatives. By comparison, occurrences of nonstandard -s in nonexistential structures did not seem to demonstrate these constraints. Investigating such constraints is instructive in several respects. First, they help to identify the nature of nonstandard -s. Second, they provide new evidence for the generative inquiry into issues relating to subject-verb agreement. Third, they delimit variable contexts for variationist analyses. In this way generative and variationist objectives meet. I will argue that researching syntactic variation necessitates combining generative and variationist methodology. © Cambridge University Press 2005.