Posterior reversible encephalopathy syndrome (PRES) is characterized clinically by headache, altered mental status, visual loss, and seizures. PRES is associated with neuroradiological findings characterized by white matter abnormalities, predominantly in the parieto-occipital regions of the brain. PRES is most often described in cases of hypertensive encephalopathy,eclampsia,renal failure,and immunosuppressive or anticancer therapy.We report a case of PRES associated with severe hypertension in the setting of a progressive renovascular hypertension from bilateral atherosclerotic renal artery stenosis.The pathogenesis of PRES is discussed and the importance of a prompt diagnosis and treatment is emphasized.