This thesis aims to develop a critical vocabulary for dealing with site-specific performances. It focuses on their association with dereliction and decay and assesses the implications of this. A central claim is that these performance modes are best understood in terms of their critical reception. I argue that site-specific performances redefine the language of criticism while profoundly questioning theatre's cultural location. Even in the cases of site-specific performances that flagrantly negate traditional theatre forms, the theatre text and critical frameworks, these return in said performances as fragmented, spectral or unconscious. The thesis divides into two parts. Part 1 deals with the emergence of site-specific performance at the intersection of trends in art and theatre in the 1960s. It outlines the role of decay and the 'found' object/space in creating a genealogy for site-specific performances, while showing how critical writing changed to map this new terrain (Chapter 1). Furthermore, it argues that site-specific performances are characterized by distinctive modes of critical writing, in which the critic is self-reflexive and creative (Chapter 2). Arguing that critics are deeply implicated in the production of site-specific performances, Part 1 ends with a critical and creative reconstruction of Deborah Warner's use of abandoned sites for performances in London in the 1990s (Chapter 3). Part 2 of the thesis re-reads the creation of Peter Brook's Bouffes du Nord and Ariane Mnouchkine's Cartoucherie de Vincennes as site-specific events which were subsequently reinscribed as the defining moment in each theatre's history. I show how site-specificity changed from being a counter-cultural gesture into a constantly redeployed marker of cultural identification. Chapter 4 examines narratives of the discovery of the two theatre venues by their directors and critics, showing how site-specificity is produced at the intersection of individual, cultural and aesthetic discourses. Analysis of the Bouffes du Nord in Chapter 5 charts the critical uses of the theatre's decay, while Chapter 6 views the Cartoucherie as the culmination of the Théâtre du Soleil's quest for group identity through identification with workers.