Chromosome 17-linked dementias have been defined by linkage analysis. The most common of these syndromes has been estimated to be the cause of between 2 and 20% of all dementia and has alternately been called frontotemporal dementia, Pick's disease (without Pick bodies) and dementia lacking distinctive features [1-3]. The identification of the mutation responsible for these conditions in a group of clinically and pathologically heterogeneous disorders may allow us to gain broad insight into the processes of neurodegeneration.