'Actors always talk about what the audience does. I don't understand, we are just sitting here.' Audience as Performer proposes that in the theatre, there are two troupes of performers: the actors and the audience. Although academics have scrutinised how audiences respond, make meaning and co-create while watching a performance, little research has considered the behaviour of the theatre audience as a performance in and of itself. This insightful book describes how an audience performs through its myriad gestural, vocal and paralingual actions, and considers the following questions: If the audience are performers, who are their audiences? How have audiences' roles changed throughout history? How do talkbacks and technology influence the audience's role as critics? What influence does the audience have on the creation of community in theatre? How can the audience function as both consumer and co-creator? Drawing from over 140 interviews with audience members, actors and ushers in the UK, USA and Austrialia, Heim reveals the lived experience of audience members at the theatrical event. It is a fresh reading of mainstream audiences' activities, bringing their voices to the fore and exploring their emerging new roles in the theatre of the Twenty-First Century.