Posterior reversible encephalopathy syndrome (PRES) is suggested in patients with acute neurological symptoms in the appropriate clinical context, including acute hypertension, blood pressure fluctuations, renal failure, blood transfusion, immunosuppression, autoimmune disorders, and eclampsia. PRES is a clinical syndrome, and refers to a disorder with reversible subcortical vasogenic brain edema caused by endothelial dysfunction, predominantly involving the bilateral parieto-occipital regions. Although the clinical course and prognosis are favorable in most cases, intracranial hemorrhage and/or restricted diffusion similar to acute infarction could be seen in some lesions on brain magnetic resonance imaging (MRI). The spinal cord may be involved in some patients with posterior fossa lesions. Understanding the pathophysiology of PRES is helpful in making the correct early diagnosis and selecting appropriate therapies to improve its clinical course and outcome. Differentiation of PRES from strokes is critical in the setting of a neurological emergency.