We have reported the family line with frontotemporal dementia (FTD) in Japan. This family line has so far included four patients. Patient II-1 (man) had a 10 year history of slowly progressive personality and behavioral changes and died at the age of 56. His neuropathological examination showed severe atrophy of the bilateral frontal and temporal cortices with neuronal loss, gliosis and superficial spongiosis. Pick bodies were not found. The neuropathological diagnosis was atypical Pick's disease without Pick bodies or Pick-type in FTD. Patient III-2 is patient II-1's oldest daughter and was taken ill with personality change at the age of 52. She died at the age of 68. Patient III-4 is patient II-1's second daughter. Her onset with strange speech and behavior was at the age of 59. Patient III-5 is patient II-1's oldest son. He also had onset with personality change at the age of 54 and had the P301L mutation in tau. In all III generation cases CT/MRI revealed circumscribed frontotemporal atrophy. Patient III-5's PET/SPECT showed signs of hypoperfusion or hypometabolism in the bilateral frontotemporal areas. This is the first report of familial FTD with the P301L mutation in Japan.