Abstract: This paper discusses factors that may contribute to the participant's sense of presence in immersive virtual environments. We distinguish between external factors, that is those wholly determined by the hardware and software technology employed to generate the environment, and subjective factors, that is how sensory inputs to the human participant are processed internally. The therapeutic technique known as neuro-linguistic programming (NLP) is used as a basis for measuring such internal factors. NLP uses the idea of representation systems (visual, auditory and kinesthetic) and perceptual position (egocentric or exocentric) to code subjective experience. The paper also considers one external factor, that is how the virtual environment represents a participant-either as a complete body, or just an arrow cursor that responds to hand-movements. A case-control pilot experiment is described, where the controls have self-representation as an arrow cursor, and the experimental group subjects as a simple virtual body. Measurements of subjects' preferred representation systems and perceptual positions are obtained based on counts of types of predicates and references used in essays written after the experiment. These, together with the control variable (possession/absence of a virtual body) are used as explanatory variables in a regression analysis, with reported sense of presence as the dependent variable. Although tentative and exploratory in nature, the data analysis does suggest a relationship between reported sense of presence, preferred representation system, perceptual position, and an interaction effect between these and the virtual body factor.