Speakers in conversation routinely engage in audience design. That is, they construct their utterances to be understood by particular addressees. Standard accounts of audience design have frequently appealed to the notion of common ground. On this view, speakers produce well-designed utterances by expressly considering the knowledge they take as shared with addressees. This article suggests that conversational common ground, rather than being a category of specialized mental representations, is more usefully conceptualized as an emergent property of ordinary memory processes. This article examines 2 separate but equally important processes: commonality assessment and message formation. Commonality assessment involves the retrieval of memory traces concerning what information is shared with an addressee, whereas message formation involves deciding how to use that information in conversation. Evidence from the CallHome English corpus of telephone conversations shows how each of these processes is rooted in basic aspects of human memory. The overall goal of this article is to demonstrate the need for a more cognitive psychological account of conversational common ground.