A 79-year-old woman had a 10-year history of dementia, initially presenting as non-fluent aphasia. Magnetic resonance imaging showed frontal atrophy (left greater than right) and hyperintense foci within white matter. Neuropathologically, there was severe frontal atrophy due to cortical neuronal loss with spongy change and to an even greater loss of white matter that contained prominent eosinophilic deposits. The deposits were immunoreactive for phosphorylated tau, non-reactive for Abeta and alpha-synuclein and equivocally or weakly reactive for ubiquitin. They stained with the Gallyas, Bielschowsky, and Bodian techniques. Ultrastructural examination revealed the deposits to be composed of straight filaments with a diameter of approximately 10 nm, primarily in white matter glia. Moderate loss of neurons in substantia nigra and numerous argyrophilic threads in gray and particularly white matter were noted. The precise relationship between this disorder and other frontotemporal degenerations/tauopathies, as well as the pathogenetic basis of the leukoencephalopathy, remains to be determined.