Acute stress disorder (ASD) is a recently developed diagnosis that describes posttraumatic stress reactions that occur in the first month following a trauma. Diagnostic criteria include dissociative, intrusive, avoidance, and arousal symptoms. ASD was driven by the proposal that trauma leads to dissociative reactions, and these are predictive of longer-term psychopathology. This paper reviews a series of anomalies in the diagnostic criteria, highlights discrepancies between criteria for ASD and posttraumatic stress disorder (PTSD), and illustrates the lack of empirical evidence for some assumptions inherent in the conceptualization of ASD. It is argued that future revisions of ASD criteria need to be based on empirical evidence of acutely traumatized individuals.