It has been shown that internally generated (thought or imagination) and externally generated (events, things, or people encountered in the past) autobiographical memories differ in characteristic ways. To examine the consequences of rehearsal on simulated perceived and imagined autobiographical memories, 36 undergraduate students participated in a 3-day experiment. During the first day, subjects perceived six situations and imagined another six situations. On the second day, subjects rated their memories for each of the situations, using a 7-point scale. They then were instructed to think about each situation 0, 4, or 8 times and were cued with an event label on each rehearsal trial. On the third day, subjects rehearsed the situations again, and rated their memories. Results showed that rehearsal affected some aspects of the memories but not others. For example, rehearsal had parallel effects on both perceived and imagined memories for all visual attributes. Perceived memories were sharper, had more colors, more visual details, and were more vivid than imagined memories. In addition, perceived memories were more detailed and more comprehensive than imagined ones, and subjects had less doubts and better overall memory for perceived than for imagined events. These findings agree with previous reality monitoring findings that people distinguish between memories for perceived and imagined events basing their judgments on the typical attributes of each type of memory. (The appendix contains the rating scale used in the study.) (KGB)