Posttraumatic stress disorder (PTSD) frequently occurs after combat and other life-threatening or traumatic events. Currently available treatments for PTSD often have a brief, limited effect, or are not well-tolerated. Motion-assisted, Multi-modular Memory Desensitization and Reconsolidation (3MDR) is a new and unique treatment for PTSD that has been commonly referred to as "walk and talk" therapy, because you walk on a treadmill as you work through your symptoms with a therapist. 3MDR also combines some features of virtual reality exposure therapy (VRET) and Eye Movement Desensitization and Reprocessing (EMDR), and has usually been conducted in the Computer Assisted Rehabilitation Environment (CAREN), a sophisticated virtual reality "cave". Previous clinical studies by us and others across several nations have proven the effectiveness of the 3MDR approach in treating symptoms of PTSD. However, the CAREN is large, expensive (\~$1 million), and only available in a few places around the world. To try to make 3MDR available to more people, this study will compare how much PTSD symptoms change with 3MDR delivered via two different mechanisms: 1) walking on a regular treadmill while wearing goggles (known as augmented reality head-mounted display, or AR HMD, specifically the Microsoft Hololens2) that allow you to see the treadmill and things around you in the real world, while also seeing pictures in a virtual world, with 2) walking on the same treadmill, with presentation of pictures on a 34-inch curved high definition gaming computer monitor positioned at eye level directly in front of the treadmill. There will be a total of 60 participants in the study, all at Uniformed Services University. After completing the informed consent process, all participants will be evaluated to confirm that they meet criteria for PTSD. There will be two introductory sessions where you meet the therapist you will be working with, and they will help you choose music and pictures that will be used in your later sessions. These introductory sessions can be done in person or virtually. In the third session you will try walking on the treadmill with a sample picture, via either the AR HMD or the computer monitor, depending on which approach you are randomized to receive-you have an equal chance of either. Starting with the 4th session, you will be talking through the pictures you have chosen, with your therapist. You will spend about 10 minutes on each picture, and do 5 or 6 pictures each session, and will do this through session 9. After that, you will complete a brief questionnaire about your symptoms. If you still have significant symptoms, you will do another 2 sessions of talking through your pictures, then do another questionnaire, and again will do two more sessions if you still have symptoms. There is then one final wrap-up session, which can be done either in person or virtually, to discuss how you did with the therapy, and whether you might need any more therapy to help you if you have any symptoms left to address. Depending on how quickly your symptoms improve, you may do a total of 10, 12 or 14 therapy sessions in this study. After you have finished the therapy sessions, you will again be assessed to see how much your symptoms have improved, and you will do this again 3 and 6 months later.