Ehlers and Clark (Behav. Res. Ther., 38 (2000) 319) recently proposed a cognitive model of posttraumatic stress disorder (PTSD). In this study, we examined two facets of this model, appraisal and peritraumatic dissociation, in the context of a hospital emergency room. Fifty-one emergency room personnel completed questionnaires measuring posttraumatic stress symptoms, interpretations of traumatic events experienced while working in the emergency room and subsequent intrusive recollections, and peritraumatic dissociation. Twelve percent of participants met formal diagnostic criteria for PTSD, and 20% met PTSD symptom criteria. As predicted, both negative appraisals of the trauma and of intrusive recollections were associated with increased PTSD severity. Although peritraumatic dissociation did not correlate with overall PTSD symptom severity, it was associated with the reexperiencing symptom cluster. Discussion focuses on the factors associated with PTSD in emergency room professionals and implications for intervention.