This study investigates forms of theatre/performance practice and training that can be seen to employ 'trance' states or engage the concept of 'states of consciousness' as performative practice. Trance is considered to be the result of sustained involvement with detailed information that is structurally organised, invoking imaginative and affective engagements that are maintained as interactions between the performer, other performers, the environment and audience of the performance. This thesis investigates trance performance through the conceptual lens of dramatic arts practice. In their respective cultural contexts, trance and theatre attain qualities considered as sacredness. Trance practice and performance, across a range of cultural contexts, are analysed as social processes - as elements of power relations that influence the performer, audience and environment of the performance. As performance traditions and events, this study will examine strands of praxis that can be drawn from Constantin Stanislavski to Lee Strasberg to Mike Leigh; from Antonin Artaud to Samuel Beckett and Jerzy Grotowski; from the Balinese trance performance form of Sanghyang Dedari in the 1930s to the 1990s; from the Channeling practitioners in the U.S. in the 1930s to Seth and Lazaris in the 1970s to the 1990s; and from traditions of military training, performance violence, and rhetoric associated with the attacks of the 11th of September 2001 in the U.S. and its aftermath.