Posterior reversible encephalopathy syndrome (PRES) is a clinical and radiographic syndrome characterized by nonspecific neurological symptoms and characteristic imaging findings of symmetrical posterior-predominant cerebral white matter vasogenic edema. There are numerous causes of PRES. However, the most common conditions associated with it are moderate to severe hypertension, preeclampsia and eclampsia, the use of immunosuppressant and cytotoxic drugs, autoimmune disorders, bone marrow, stem cell or solid organ transplantation, infection with sepsis and shock, and acute or chronic kidney disease. The precise pathophysiological mechanism behind PRES has yet to be fully clarified. However, the generally accepted mechanism is dysfunction of the blood-brain barrier resulting in vasogenic edema. There are several proposed theories for the pathophysiology of PRES. One of them is the hypertensive and cerebral hyperperfusion theory which proposes that the primary cause of vasogenic edema is the loss of autoregulation in the posterior circulatory area of the cerebral vascular system due to large and sudden increases in blood pressure. The second major theory is the endothelial dysfunction theory, which proposes endothelial injury caused by circulating toxins as the primary cause of PRES, which leads to the increased permeability of the blood-brain barrier and the development of vasogenic edema. Clinical presentation is nonspecific and ranges from headache and impaired visual acuity to visual loss, epileptic seizures, altered mental status and altered levels of consciousness in more severe cases. T2-weighted/FLAIR sequences on MRI play a fundamental role in the diagnosis of PRES and are most useful in detecting vasogenic edema and in differentiating PRES from other medical conditions that share some clinical and pathophysiological features. PRES may occur on imaging in an atypical fashion with the involvement of basal ganglia, brainstem, or cerebellum, or it may be complicated by the presence of cerebral hemorrhage or cytotoxic edema. PRES is usually reversible, and the treatment is aimed at eliminating the cause if possible. Prognosis is good if the cause is recognized and removed, and most patients show clinical improvement and regression of lesions on follow up brain MRI within a few weeks.