Recent advances in brain imaging have permitted an examination of alterations in brain function in patients with post-traumatic stress disorder (PTSD). This chapter reviews findings from neuro-chemical and neuroreceptor brain imaging measured with positron emission tomography (PET), single photon emission computed tomography (SPECT) and magnetic resonance spectroscopy (MRS). Neurochemical brain systems involved in the stress response are also affected by PTSD. These include norepinephrine, the hypothalamic-pituitary-adrenal (HPA) axis, serotonin, opiate and benzodiazepine systems. Using magnetic resonance imaging (MRI), it is possible to measure the physical properties, or spectra, of individual chemicals in the brain. Brain imaging studies are consistent with dysfunction of the hippocampus and anterior cingulate in PTSD. Several studies have looked specifically at neurochemical alterations in the hippocampus, and some have also looked at the anterior cingulate, most using N-acetyl-aspartate (NAA) as a marker of neuronal integrity.