The stress associated with experiencing or witnessing physical trauma can cause abrupt and marked alterations in mental state, including anxiety and transient dissociative symptoms. Intense manifestations of this pattern of response to trauma are described in a new diagnostic category proposed for DSM-IV: acute stress disorder. Severe dissociative symptoms may predict subsequent posttraumatic stress disorder. Persons who experience a series of traumatic events may be especially vulnerable to a variety of dissociative states, including amnesia, fugue, depersonalization, and multiple personality disorder. Treatment for these symptoms emphasizes strengthening supportive interpersonal relationships and developing insight that reduces psychological pain by integrating the trauma into a meaningful, less self-blaming perspective.