Frontotemporal dementia (FTD) is the second most frequent degenerative cause of dementia. Although described for more than a century, it remains often misdiagnosed, mistaken for Alzheimer's disease or psychiatric disorders, which is prejudicial to care and research. It is a clinical syndrome corresponding to at least three histological entities: (1) Pick's disease, (2) non-specific frontotemporal degeneration, (6 times more frequent), and (3) frontal lobe abnormalities associated with motor neurone disease. It never corresponds to Alzheimer pathology. It must be suspected in patients with behavioural dyscontrol predating memory impairment, without spatial disorientation and normal EEG.