Examples are reported of PTSD cases showing full symptomatology (intrusive imagery, avoidance behaviour, disordered arousal) in the absence of a single, acute, dramatic trauma of the kind required by the current DSM-III-R definition. Such trauma is thus not a necessary condition for PTSD, and other evidence shows it to be not a sufficient condition. It is suggested that the DSM-III-R Axis IV distinction between acute and enduring psychosocial stressors be incorporated into the definition to distinguish two pathways to stress disorder, post-traumatic (PTSD) and prolonged duress (PDSD). Differential treatment implications of the two routes are noted.