Periventricular hyperintensity was identified using long repetition and echo times in spin-echo magnetic resonance imaging of patients with white-matter disease (e.g., multiple sclerosis) caused by local demyelination and in hydrocephalic patients caused by transependymal migration of spinal fluid. A review of 365 consecutives studies revealed that some degree of periventricular hyperintensity is present in most patients (93.5%) regardless of diagnosis. Mild periventricular hyperintensity was seen in patients with no other evidence of intracranial pathology. Periventricular hyperintensity is a normal finding that should not be considered indicative of either demyelinating disease or hydrocephalus. More extensive and severe periventricular hyperintensity is associated with intracerebral pathology, but the finding often is nonspecific. For example, mild periventricular edema from hydrocephalus is impossible to differentiate from the increased periventricular hyperintensity seen in patients with multiple white-matter lesions. Thus, the pattern of periventricular hyperintensity has proven to be of limited value in the clinical assessment of hydrocephalic patients.