Frontotemporal degeneration (FTD), one of the most prevalent causes of presenile dementia, includes three subtypes: (1) behavioral variant FTD (bvFTD), (2) semantic variant (SV), and (3) progressive nonfluent aphasia (PNFA). Corticobasal degeneration, progressive supranuclear palsy, and FTD-ALS are linked clinically and pathologically to FTD. The clinical presentation of these FTD-related disorders comprises a wide spectrum, including behavioral and psychiatric symptoms, aphasia, motor neuron findings, and parkinsonism. Two types of proteinopathies, tau and TAR DNA-binding protein 43 (TDP-43), are seen in most cases at autopsy. Mutations on the genes for tau and progranulin on chromosome 17 each account for 5% to 10% of familial FTD cases. Imaging reveals focal bifrontal atrophy and hypometabolism in bvFTD, asymmetric bilateral anterior temporal lobe changes in SV, and left perisylvian abnormalities in PNFA. Treatments for FTD are under active investigation and may soon reach clinical trials.Continuum Lifelong Learning Neurol 2010;16(2):191-211.