The diagnostic evaluation of dementia is directed toward the identification of treatable causes. It can be facilitated by classification of the dementia into one of four categories: attentional, amnestic, cognitive, and intentional. Intentional dementia reflects dysfunction of frontal lobe systems, components of which include the frontal cortex, basal ganglia, thalamus, limbic structures, and subcortical white matter. Disorders that affect one or more of these components and produce intentional dementia include Binswanger's disease, Parkinson's disease, Huntington's disease, HIV infection, closed head injury, normal pressure hydrocephalus, neoplasms, syphilis, vitamin B12 deficiency, multiple sclerosis, and a number of uncommon degenerative and acquired syndromes. Depression may resemble intentional dementia. Guidelines for diagnosis and management are discussed.