The authors define trauma as an abrupt physical disruption in ordinary daily experience. The individual feels fear, abject helplessness, or horror stemming from the sense of having lost control. Less frequently, people respond to trauma with rage or guilt. Post-traumatic stress disorder is classified as an anxiety disorder in DSM- III-R, and the focus of treatment becomes mastering that affect. Clinicians may consequently overlook the prevalence of dissociative defensive constellations against the overwhelming stress of the traumatic event—including multiple personality disorder, psychogenic amnesia, psychogenic fugue, and simple dissociation. To recognize this large number of dissociative responses to trauma, a new diagnosis, acute stress disorder, has been proposed for DSM-IV. The authors present eight criteria