Post traumatic stress disorder (PTSD) is a common and disabling condition that often goes undiagnosed for years, and even when the diagnosis is made, treatment is frequently ineffective, especially for combat veterans. Cognitive behavioural therapy with imaginal exposure is considered first-line treatment, but many can not or will not engage in imaginal exposure, which is not surprising, since avoidance of reminders of the trauma is a defining feature of PTSD. Novel technologies offer an alternative to facilitate exposure therapy, through virtual reality (VR). This book outlines state of the art approaches to improving the diagnosis and treatment of PTSD, with a particular emphasis on the promise and pitfalls associated with VR exposure therapy. The world's leading experts in this cutting edge field describe their VR work in phobias and other mental disorders, and chart a course for future studies to improve the diagnosis and treatment of PTSD.