Dementia with Lewy bodies (DLB) is the second most frequent neuropathologically diagnosed degenerative dementing illness. The clinical characteristics are progressive dementia, parkinsonian syndrome, fluctuations of cognitive functions, alertness, and attention, visual hallucinations (usually detailed and well described), depression, REM sleep behavior disorder, adverse responses to standard neuroleptics doses, falls, syncopes, systematized delusions, and other modalities of hallucinations. Specificity of the clinical diagnostic criteria is high (95%), and sensitivity is considerably lower. Mean age at disease onset ranges between 60 and 68 years. The male gender prevails. Disease duration is 6 to 8 years. The differential diagnoses of DLB are dementia of the Alzheimer type, Parkinson's disease, subcortical arteriosclerotic encephalopathy, progressive supranuclear palsy, multiple system atrophy, and rarely Creutzfeldt-Jakob disease. The genetic background of the disease is unclear. Magnetic resonance imaging and single photon emission tomography can contribute to the diagnosis. Controlled pharmacological studies have so far not been published. The disease is treated with L-dopa, atypical neuroleptics, acetylcholine esterase inhibitors, antihypotensive agents, and peripheral anticholinergic and alpha receptor-blocking medications to improve neurogenic bladder dysfunction.