This article provides an overview of the relationship between studies of syntactic variation in dialects of English and theoretical accounts of language structure. In the first section of the article, we provide a discussion of the place of syntactic variation within various subdisciplines of linguistic enquiry: we address issues such as I- and E-language, the place of Standard English in linguistic theory, and interfaces between traditional dialectology, variationist sociolinguistics, and theoretical linguistics. These interfaces suggest the need for a clarification of the nature and status of the (morpho)syntactic variable, which we provide in section 3; and in section 4, we examine the way in which (morpho)syntactic variation is treated within a number of theoretical models – for instance, Principles and Parameters theory, HPSG, OT, and cognitive linguistics (including Word Grammar and Construction Grammar) – all of which feature in the other articles in this special issue.