This report concerns a 71-year-old woman who had rapid progressive dementia along with myocloni and increased blood pressure. Cranial computed tomography and magnetic resonance imaging scans showed bilateral widespread white matter changes with mass effect. A brain biopsy revealed an amyloid angiopathy in leptomeningeal as well as cerebral cortex arteries. After 2 months of antihypertensive treatment, a dramatic improvement of cognitive functions and a spectacular regression of leukoencephalopathy were observed. We suggest that hypertensive encephalopathy may worsen or reveal cerebral amyloid angiopathy.