This chapter addresses interactional sociolinguistics as one of the key antecedents and theoretical influences on the development of linguistic ethnography. It focusses in particular on the work of John Gumperz, while also addressing Hymes’ influence. It begins by describing the historical origins of interactional sociolinguistics, situating these in relation to Gumperz and Hymes’ efforts to produce a general theory of language and society. The chapter addresses key theoretical notions including inference and contextualisation. It explores the relationships between interactional sociolinguistics and other related fields, including linguistic anthropology and conversation analysis. It demonstrates and argues for the value of the close analysis of recorded interaction. It goes on to explore how interactional sociolinguistics has been drawn on in contemporary research on stylisation and on asylum procedures, and highlights future possibilities of using interactional sociolinguistic approaches in studying important contemporary phenomena such as digital interaction and new forms of surveillance.