Clinically, dementia with Lewy bodies is characterized by a gradually progressive dementia syndrome with at least two of the following three cardinal features: 1) fluctuations in cognition, 2) visual hallucinations, 3) parkinsonism. Supportive clinical features include exaggerated response to neuroleptic medications, delusions, gait disturbance, and episodes of loss of consciousness. The disorder is unique among neurological illnesses in having a psychiatric criterion—visual hallucinations—as a diagnostic feature and, as such, demonstrates the progressive integration of neurobehavioral and neuropsychiatric features into our understanding of dementing illnesses. Pathologically, dementia with Lewy bodies features multiple neuritic plaques similar to those seen in Alzheimer’s disease as well as brainstem and cortical Lewy bodies. There are relatively few neurofibrillary tangles. The patients tend to respond relatively well to treatment with cholinesterase inhibitors, and when psychotropic agents are required to control delusions and agitation, novel antipsychotics are preferred.