Although scholars have studied some sources of variation within genres, the variation that is each individual performance of a genre requires further investigation. In Genre Analysis, John Swales combined rhetoric and linguistics to explain genre as grounded in shared communicative purposes and discoverable through text analysis. Although the disciplines differ in some of their purposes and settings, they share the difficulty of helping students advance beyond simplified understandings of genre to the complex decisions needed to address particular situations. Building from a rhetorical-linguistic genre studies and using metaphorically the linguistic concepts of competence and performance, this article proposes that genre theory and instruction should account for genre performances as well as genre competence. Genre theory can then better address such issues as identity, affect, and cognition. Genre instruction can lead students to examine not just similarity within a genre but also differences, in both communicative event and individual language-users. The uniqueness of each performance also affects assessment of genre knowledge and transfer, complicating the ability to assess genre competence through genre performance. Considering genre performances as well as competence within a rhetorical-linguistic genre studies allows genre scholars and teachers to address the fact that genre-in-use is simultaneously unique and shared.Scholars within genre studies have investigated many sources of variation within a genre. While still based theoretically in understandings of the shared nature of genres-whether shared social actions (Miller, 1984), communicative purposes (Swales, 1990), or social processes (Martin, 1997)-genre scholarship has A. Devitt, Genre Performances 2 demonstrated that texts within those genres vary in their prototypicality (Paltridge, 1997); across dimensions of textual clusters (Biber, 1988); by discipline (Soliday, 2011;Hyland, 2012); and historically (Bazerman, 1988; and many others). Research on genres in the schools has found that students' genre knowledge and acquisition vary, among other things, by socio-economic class (Spinello & Pratt, 2005;Myhill, 2005). An individual's patterns of variation across texts have been described as well, in every literary or rhetorical study of an author's style but notably also in linguistic studies of individual personas (Hyland, 2010(Hyland, , 2012. At times, scholars refer to particular "performances" of a genre (Bawarshi & Reiff, 2010) or "performing" identity within disciplinary conventions and community repertories (Hyland, 2010).All such scholarship recognizes and helps to account for the variation that necessarily occurs every time someone performs a genre in a particular text. At the heart of all such variation is the fact that genres are at once shared and unique. Each performance of a genre demonstrates its degree of prototypicality, disciplinary membership, historical moment, authorial identity, and many other qualities shared with other memb...