To the Editor: We read with interest the timely article by Dr. Marshall et al. on the newly proposed diagnosis of acute stress disorder and were dismayed by the conclusion that dissociation should be eliminated as a core symptom of acute stress disorder. The usefulness of acute dissociation in predicting PTSD is a complex topic containing several possible roles for dissociation: as a sole predictor, as the most important predictor, as a valuable additional predictor that adds prognostic information, or as an associated feature of limited specific value. Prediction in itself is complicated and encompasses sensitivity, specificity, and positive and negative predictive values. Reports on the topic typically address only aspects of these questions, and the authors do not systematically flush these out, as if set on disproving the importance of many positive findings regarding dissociation.