Four issues of key interest with regard to posttraumatic stress disorder in the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) are discussed. These include: (a) how to define the stressor criterion, especially, whether or not the victim's response ought to be included and whether low-magnitude traumas qualify etiologically; (b) the cohesiveness of the syndrome and the validity of items across stressor groups; (c) the position of posttraumatic stress disorder within DSM-IV; and (d) comorbidity with other illnesses.