Post-traumatic stress disorder (PTSD) is one of the anxiety disorders recently included in the Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM-III).(1) The disorder refers to the psychological sequelae that may follow a significant stressor. The military has previously referred to PTSD as "war neurosis," "shell shock," and "combat neurosis."PTSD has recently gained attention as a means of legal defense. As a defense, it may exist separately from "innocence by reason of insanity." The authors review the literature, provide case vignettes exemplifying the clinical features, and present three additional cases that gained local and national notoriety because of their defense motions. The senior author served as an expert witness in these cases. Recommendations are given to readers who may in the future serve as expert witnesses or consultants in similar cases.