OBJECTIVE: The author's goal was to explore the historical, political, and social forces that have played a major role in the acceptance of the idea of trauma as a cause of the specific symptoms of posttraumatic stress disorder (PTSD) and to discuss the impact that current research findings have had on some of the initial conceptualizations of the disorder. METHOD: The conceptual origins of PTSD are described, and the literature on the prevalence, longitudinal course, phenomenology, and neurobiology of PTSD is reviewed. RESULTS: Paradoxically, there are a series of findings that support the idea that PTSD is a distinct diagnostic entity, but these are different from those originally developed from psychosocial theory and stress research. CONCLUSIONS: PTSD has been a controversial diagnosis and is again at a vulnerable point. It is imperative that the field address how current findings challenge the original conceptualizations of this disorder so that the next generation of conceptual issues can be formulated.