A key goal in the development of virtual reality games (virtual environment, simulation, and edutainment are all included) is to increase presence of the player. This is usually accomplished by reinforcing the player’s sense of spatially “being there” or what is termed immersion in the technological aspects of the game. Interestingly, there are not many well validated measures of “presence” (nor immersion) and there is considerable debate in the field as to how presence should be assessed; using behavioral markers like galvanic skin response or eye movement versus self-report. Several recent studies propose psychometrically refined instruments (paper-and-pencil) to assess presence. LARS is currently working in this area to assess presence in youth as they engage in a virtual environment drug prevention program.