Following exposure to trauma, a large number of survivors will develop acute symptoms of posttraumatic stress disorder (PTSD), which mostly dissipate within a short time. In a minority, however, these symptoms will evolve into chronic and persistent PTSD. A number of factors increase the likelihood of this occurring, including characteristic autonomic and hypothalamic-pituitary-adrenal axis responses. PTSD often presents with comorbid depression, or in the form of somatization, both of which significantly reduce the possibilities of a correct diagnosis and appropriate treatment. Mainstay treatments include exposure-based psychosocial therapy and selective serotonin reuptake inhibitors, such as paroxetine and sertraline, both of which have been found to be effective in PTSD. This paper looks at the course of PTSD, its disabling effect, its recognition and treatment, and considers possible new research directions.