Post-Traumatic Stress Disorder (PTSD) is a common and severe psychiatric disorder precipitated by exposure to a psychologically distressing event. PTSD is associated with significant morbidity and mortality and is characterised by the presence of three distinct, but co-occurring, symptom clusters. Research evidence suggests that PTSD has a neurobiological basis. Current research on the neurobiology of PTSD include the utilisation of functional brain imaging; molecular genetic research; and, the incorporation of cross-system research including neuroendocrine, neurochemical, and neuroimmunological systems. This book examines the neurobiological basis of PTSD and the future research goals in regards to these findings.