Post-traumatic stress disorder (PTSD) is a psychiatric disorder that is common in the general population. PTSD symptoms include re-experiencing the traumatic event, avoidance of reminders of the trauma, and increased arousal. The primary treatments of PTSD are psychotherapy and antidepressant medications. While both are effective, many patients continue to have significant symptoms. Repetitive Transcranial Magnetic Stimulation (rTMS) is a new research and treatment modality that uses a small powerful electromagnet to directly stimulate the brain. This stimulation may increase or decrease brain activity. The treatments have been shown to be effective in other disorders such as depression. Initial treatment of patients with PTSD using rTMS has been hopeful. This study is the first randomized controlled trial to examine the efficacy of rTMS for PTSD.