Thanks to the recent developments in the theory of academic discourse analysis, it is now increasingly accepted that negotiation of academic knowledge is intimately related to the social practices of academic communities. To underpin this position and to reveal some of the ways this is achieved, this article analyzes a relatively wide spectrum of academic texts (20 research articles, 20 handbook chapters, 20 scholarly textbook chapters, and 20 introductory textbook chapters) in applied linguistics. The authors show here the importance of establishing social relationships in academic arguments, suggest some of the ways this is achieved, and indicate how the social and institutional differences that underlie production and reception of different academic genres influence the ways metadiscourse is shaped in academic communication. (Contains 7 tables and 2 figures.)