PTSD is a mental disorder which may occur under the stress of a traumatic event, which includes war experiences suffered by many Vietnam veterans. The best-known PTSD symptom is the re-experiencing of the traumatic event, which may involve powerful recollections, recurrent dreams, or acting-out behavior as though the event were occurring. Although statistics show a disproportionate number of Vietnam veterans in the criminal justice system, there is no conclusive data to link PTSD directly to criminal conduct. PTSD's prevalent uses in the legal context are as an insanity defense, grounds for a new trial, and as a mitigating sentencing factor. PTSD is not likely to qualify under prevalent insanity defense rules. It is more likely to qualify under a diminished capacity defense, but this defense is not recognized in all States. PTSD's value as grounds for a new trial may also vary from jurisdiction to jurisdiction. The use of PTSD by Vietnam veterans as a mitigating factor in sentencing will depend for success on the personal feelings of a judge or jury toward Vietnam veterans. Possible approaches for dealing with PTSD in a legal context are to provide special corrections treatment programs for Vietnam veterans; a more uniform and systematic application of PTSD as a sentencing factor; and a reexamination of rules for granting a new trial based on new evidence, including a recent diagnosis of PTSD. 252 footnotes.