Dementia with Lewy bodies (DLB) is increasingly recognized as a distinct clinical and pathologic entity. It is a progressive dementia characterized by persistent and well-formed visual hallucinations, marked second-to-second fluctuations in attention, and progressive extrapyramidal signs. The diagnostic value of additional clinical features such as delusions, depression, falls, anosmia, and rapid progression continues to be debated. Despite the growing acceptance of the diagnosis, DLB has not yet been included in either International Classification of Disease (ICD-10) or Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria. However, the existing consensus diagnostic criteria continue to be validated. Most prospective studies to date indicate that their performance is acceptable, with specificity similar to the present diagnostic criteria for Alzheimer's disease. Nevertheless, at least one in five patients with DLB will continue to be misclassified.