The authors report a case of a young woman with progressive subcortical vascular encephalopathy without hypertension.She had no known risk factors for cerebrovascular disease.All known causes of progressive subcortical vascular encephalopathy in young patients without hypertension were eliminated by laboratory investigation.Magnetic resonance imaging revealed diffuse white matter injury, and single photon emission computed tomography showed a decrease in cerebral blood flow mainly in the white matter and temporal cortex bilaterally.In addition to recently described causes of subcortical ischemia in young and middle-aged individuals, other etiologies still remain to be identified.