Posttraumatic stress disorder (PTSD) is a chronic and disabling anxiety disorder that occurs after a traumatic event. It is associated with an increased risk of suicide and marked deficits in social and occupational functioning. Currently, the diagnosis for PTSD is established on the basis of a patient's clinical history, mental status examination, duration of symptoms, and clinician administered symptom checklists or patient self-reports. However, there are no available laboratory biomarker tests for PTSD. To begin intervention at the earliest possible time, priority must be given to developing objective approaches to determine the presence of PTSD. Thus, a simple blood test or a biomarker that could detect PTSD in its earliest and potentially most treatable stages would be beneficial for physicians and patients. Currently, many potential biomarkers have been identified in the animal model or in patients with PTSD. But those biomarkers have not been well validated. Here, we hypothesize the development of a strategy for the identification of a biomarker for PTSD. This strategy involves pre-clinical screening, analytical validations and clinical validations. This strategy will enhance not only the study of the molecular mechanisms of PTSD, but also the translation of basic science to clinical implications.