Background: Frontotemporal dementia (FTD) is a pathologically heterogeneous group of presenile neurodegenerative disorders, with or without the deposition of hyperphosphorylated tau protein in affected brain regions. Mutations in the tau gene have been found in the familial form of FTD, linked to chromosome 17q21-22, showing a spectrum of tauopathy. Objective: To evaluate levels of total tau, phosphorylated tau 181 (Ptau-181), and amyloid-β 1-42 in the cerebrospinal fluid (CSF) of patients with FTD, with special emphasis on FTD due to tau mutations. Design: Case-control study. Setting: Outpatient neurology clinics at 2 university medical centers, in Rotterdam and Amsterdam (the Netherlands). Patients: Twenty-six patients with FTD (9 with tau mutations 7 P301L and 2 G272V), 18 patients with Alzheimer disease (AD), and 13 nondemented controls. Methods: Total tau, Ptau-181, and amyloid-β1-42 levels in CSF, obtained by lumbar puncture, were determined by sandwich enzyme-linked immunosorbent assay. Patients were diagnosed after clinical examination, neuropsychologic evaluation, and neuroimaging. Differences between patient groups were statistically evaluated using nonparametric tests. Results: Although CSF levels of total tau were mildly increased in FTD patients compared with nondemented controls (P = .05), median CSF total tau levels were low in the subgroup with tau mutations compared with AD patients. Furthermore, CSF levels of Ptau-181 and amyloid-β1-42 were not different in FTD patients, including the patients with tau mutations, compared with nondemented controls. Conclusions: The tauopathy in P301L and G272V does not appear to be associated with an evident increase in CSF levels of Ptau-181 in FTD patients with these tau mutations, in contrast with findings in patients with AD.