Combat related Posttraumatic Stress Disorder (PTSD) is the most common chronic psychiatric disorder in the veteran population. Unfortunately, outcome studies of VA PTSD programs have failed to show efficacy. VA PTSD patients have been significantly less responsive to conventional therapies than other PTSD populations. Virtual Reality based exposure therapy (VRE) allows patients to feel immersed in highly interactive computer-generated environments. Within these environments patients can be exposed to anxiety-provoking stimuli in a gradual and controlled manner so that they can become desensitized to these stimuli and, in the case of PTSD, the traumatic memories evoked by these stimuli. The advantages of VRE include less reliance on the patient's ability to visualize traumatic memories and making it more difficult for patients to avoid memories during exposure therapy. It is also safer and more convenient than in vivo exposure. In this study twenty Vietnam veterans are randomly assign to either VRE or to a Treatment as Usual (TAU) control condition. Treatment would consist of ten ninety-minute individual psychotherapy sessions for both groups. Assessments would occur at pre-treatment, immediate post-treatment and at six months post-treatment.