The main aim of this project is to evaluate the use of a specific Yoga technique of controlled breathing in Vietnam War Veterans with chronic posttraumatic stress disorder. This method is currently the subject of a United States grant application to formally test American War Veterans from Afghanistan and Iraq. Drs Gerbarg and Brown are collaborating with The Bay Pines Veterans Administration Medical Center in Florida to develop a study of this course for treatment of American veterans returning from Afghanistan and Iraq. Elements of this method have been used on a variety of populations. Whilst this is a multi-component intervention, it is postulated that the most active ingredient in the program is a specific Yoga breathing technique called Sudarshan Kriya (SK).