Treatment using bright light exposure was carried out on six aged subjects with dementia in two nursing homes. Sleep logs were recorded by the staff. Bright light treatment was applied in the late morning every day. The %sleep in the lights-out period and/or the %wake in daytime increased in three subjects. In the other three subjects, sleep onset time was advanced. In all subjects abnormal behavior episodes around the lights-out time tended to be reduced. These results suggest that bright light treatment is effective in improving the sleep-wake disturbances of aged individuals with dementia.