Frontotemporal dementia refers to a diverse group of conditions that collectively are a major cause of young onset dementia Frontotemporal dementia produces selective brain atrophy involving the frontal and temporal lobes, requiring brain magnetic resonance imaging for accurate diagnosis Clinically, these diseases present chiefly as progressive aphasia or as disintegration of personality and behaviour that may be misdiagnosed as a psychiatric disorder Up to around a quarter of cases arise from dominant mutations in one of three major causative genes Frontotemporal dementia is commonly associated with other neurological impairment, in particular parkinsonism or motor neurone disease Treatment remains supportive, but patients and families need extensive counselling, future planning, and involvement of social and mental health services Sources and selection criteria We examined recent literature on frontotemporal dementia, targeting full text English language studies published since 1990. We selected articles on the basis of our personal knowledge and searches of the Medline database using the terms "frontotemporal dementia," "frontotemporal lobar degeneration," "progressive nonfluent aphasia," "semantic dementia," and "logopenic aphasia," and each of these terms in conjunction with "diagnosis," "treatment," and "therapy." The final selection of references was based on our judgment of relevance, completeness, and compatibility with recent clinical, pathological, and genetic criteria.