We report the histopathological and immunohistochemical findings in a patient with primary progressive aphasia and abnormally ubiquitinated neurites in the cerebral cortex. Neuropathological examination showed severe neuronal loss and astrocytosis with a spongy change in the frontal cortex and neostriatum. Immunohistochemistry for ubiquitin antibody showed many immunoreactive dystrophic neurites in the superficial layer of the affected cortices and putamen. Those neurites were neither argentophilic nor stained with other antibodies against neurofilament, tau, or microtubule-associated protein-2. There were no neuropathological changes characteristic of Alzheimer's disease, Pick's disease, or Creutzfeldt-Jakob disease. Immunoelectron microscopy using anti-ubiquitin antibody showed inclusions in the dendrites, consisting mainly of granular and filamentous material. These pathological features, unusual in primary progressive aphasia, indicate the neuropathological heterogeneity of this disease condition.