Although white matter lesions (WMLs) are among the most common structural neuroimaging changes found on computed tomography and magnetic resonance imaging of older persons with dementia, their presence should not be misconstrued as proof that vascular disease is causing or contributing to the dementia. We report the results of several studies examining the neurobehavioral manifestations of persons meeting explicit operational criteria for Binswanger's disease (BD) and the clinical correlates of white matter changes in persons with autopsy-proven Alzheimer's disease (AD). The findings suggest that relative to persons with AD of comparable dementia severity, persons with BD have less profound impairments in episodic memory, more depressive symptomatology and a more variable rate of cognitive decline; among persons with AD, some WMLs are associated with incontinence and gait disturbance, but they do not appear to contribute to dementia severity.