Dementia with Lewy Bodies (DLB) is an entity which now fulfils clinical and neuropathological criteria according to international consensus guidelines (McKeith et al., 1996). It is now possible, in clinical practice, to consider the diagnosis of DLB from the beginning of the management of a demented patient. The clinical, diagnostic and therapeutic aspects of DLB are investigated in a prospective manner. Visual hallucinations, fluctuations and extrapyramidal symptoms seem to have, in association with the progressive cognitive decline, some particularities. However their specificity should be correlated with neuropathological data. Other symptoms, such as repeated falls or syncope, neuroleptic sensitivity, systematized delusions or other modalities of hallucinations, are probably additional arguments giving more predictive value to the association of the major symptoms. The role of neuropsychological patterns at the beginning of the cognitive decline is shown. There are some recent concordant results of functional imaging in DLB. The neuropathological aspects of DLB and the links with Parkinson pathology and especially Alzheimer pathology are emphasized.