Delirium is more common in older adults because of normal physiologic changes, increased incidence of medical illnesses, and increased medication use in this population. Older dementing patients are particularly predisposed to delirium because of associated neurologic abnormalities. Delirium often is superimposed on a dementing condition and may be difficult to differentiate from atypical dementia or a catastrophic reaction. Accurate diagnosis is essential, as is a thorough search for an underlying cause. The delirium will usually resolve if the underlying cause is properly treated. Treatment also requires maintaining a comfortable environment for the patient and, when necessary, administering a high-potency neuroleptic.