This essay stresses two principal areas of analytic concern in conversation analysis: ‘position and composition’, or the relationship between turns at talk in specific sequences, and the design features of individual turns within sequences. Of course, other subfields within or related to the pragmatics tradition have been interested in these ‘syntagmatic’ and ‘paradigmatic’ dimensions of language use. Central to the originality of CA is the fact that it is not primarily interested in one or other of these elements, but specifically in the interrelationships between them. This is what has made conversation analytic insights so valuable to linguists, sociologists, psychologists, anthropologists, and indeed all those interested in social interaction; through exploring these relationships, CA reveals an institutionalized substratum of rules and procedures by reference to which conversationalists engage in recognizable, coherent and accountable interaction. And this is a form of social organization which is at the heart of the pragmatic enterprise: the description of language as a vehicle of social action.