Semi-quantitative neuropathological analysis and morphometric evaluations of the brains of 5 elderly people (63-85 years old) dying following a 5-27-year history of dementia reveal that, despite exhaustive survey of all major brain regions, 4 of these cases show virtually no histopathological lesions of Alzheimer's disease. Instead their CNS manifests a severe, bilateral, neuronal depletion, and astrogliosis afflicting the lateral temporal neocortex, highly compatible with a previous herpetic viral encephalitis. In the fifth case unilateral neocortical temporal lobe sclerosis is accompanied by Alzheimer's disease, but with much more dense Alzheimer lesions throughout the contralateral cerebral hemisphere. Three of these 5 individuals had a history either of herpes zoster of the skin or of a single episode of viral meningoencephalitis, roughly concomitant with the onset of memory loss. This clinical and pathological evidence that a remote herpes virus encephalopathy (when bilateral) "protects" that brain against Alzheimer's disease strengthens our growing suspicion that incomplete replication cycles of herpes simplex or zoster virus, following repeated reactivation within neurons of the trigeminal ganglia, may link these viruses to the pathogenetic cascade underlying dementia of the Alzheimer type.