Peritraumatic dissociation describes alterations in awareness that occur during or immediately after a trauma. This study investigated a simulated form of peritraumatic dissociation by indexing the responses of skydivers ( N=100) who were participating in their first skydive. Prior to jumping, participants completed the Beck anxiety inventory, the Tellegen absorption scale, and ratings of predictability and uncontrollability. Immediately after the jump, they completed the peritraumatic dissociative experiences questionnaire and the physical reactions scale. Responses indicated that the skydive elicited extreme anxiety, hyperarousal, and peritraumatic dissociation in a significant proportion of skydivers. Multiple regression analyses indicated that hyperarousal, and to a lesser extent anxiety, were strongly predictive of peritraumatic dissociative reactions. These results are discussed in terms of proposals that peritraumatic dissociation is mediated by hyperarousal.