Frontotemporal dementias with parkinsonism linked to chromosome 17 (FTDP-17) are hereditary tauopathies affecting at least 50 known kindred worldwide. Most kindred present with severe behavioral or psychiatric manifestations progressing to dementia, while some kindred first manifest a parkinsonian-plus syndrome. Nine missense mutations, one deletion mutation, and two transition mutations not altering the encoded amino acid, have been described in or near the microtubule-binding domains within exons 9, 10, 12, and 13.