Actors often report that during acting their conscious experience is altered. Many are, in fact, drawn to acting by their desire for this experience of heightened awareness. This paper will use notions from the field Psychology of Consciousness, including an explanation of how psychologists define and investigate Altered States of Consciousness (ASCs). Following the definition in The Psychology of Consciousness by Farthing, the author argues that actors (in performance, drama classes, or in psychodrama) routinely enter an ASC. Acting is seen as altering most of the 14 dimensions of changed subjective experience which characterise ASCs according to Farthing, namely: attention, perception, imagery and fantasy, inner speech, memory, higher-level thought processes, meaning or significance of experiences, time experience, emotional feeling and expression, level of arousal, self-control, suggestibility, body image, and sense of personal identity. This result is established by drawing on the writings of theatre theorists, actors, directors, educators, drama therapists, and psychodramatists. The theoretical observations are supported by empirical findings from studies in which actors are given questionnaires to capture their subjective experience during acting. After establishing acting as a way to enter an ASC, there is discussion on why theatre artists, educators, and advocates need to be aware of both the dangers and benefits of experiencing altered states.