Neoplastic angioendotheliosis is a rare, severe, disease characterized by neoplastic proliferation of mononuclear cells within the lumen of small blood vessels. The clinical signs are usually dermatological and neurological. We report the case of a 57 year old woman who died after 20 months of subacute dementia. She had had also transient recurrent episodes of right paresthesiae and paresis. CSF proteins were increased. MRI showed areas of high signal in the white matter. Post-mortem showed widespread ischemic lesions, mainly in the subcortical white matter. Microscopically there was marked proliferation of cells in most CNS blood vessels. Similar cells were present in adrenals, liver, uterus, lungs and kidneys. Immunohistochemical studies showed intensive staining for leukocyte common antigen and negative staining for factor VIII-related antigen, a specific endothelial cell marker.