A German translation of the revised Impact of Event Scale (Weiss & Marmar, 1996) is introduced as a self-report questionnaire for post traumatic stress reactions and statistically tested. Three subscales - intrusion, avoidance, and hyperarousal - measure different aspects of reactions to, or symptoms of extreme stress. Analyses are based on two samples of former political prisoners in East Germany (N = 128) and crime victims (N = 30). Post traumatic stress symptoms were assessed in parallel by a structured clinical interview. Results showed sufficient degrees of reliability, validity, and diagnostic sensitivity. We propose an estimation equation for diagnostic purposes which has been cross-validated with the two samples. Problems with factorial validity and the underrepresentation of numbing symptoms are discussed.