Investigates whether subjects could separate memories of events experienced in virtual reality from real and imagined events: a decision process we term 'virtual-reality monitoring'. Participants studied 8 separate spatial configurations of red geometric objects arranged on a life-sized chessboard, 8 configurations in virtual reality (an immersive, computer-simulated world), and imagined objects in 8 other configurations. On a later source identification memory test, subjects were generally able to correctly identify the sources of the events. A 'memory characteristics questionnaire' was administered to assess differences in qualitative characteristics of memories for virtual, real and imagined events. Differences were found that could potentially serve as cues to help people decide where their memories originated. Results are interpreted within the Johnson-Raye (1981) theoretical framework.