Kosaka (1993) reviewed 16 cases of slowly progressive presenile cortical dementia thought to be a clinicopathological entity with pathological features characterized by circumscribed lobar atrophy, diffuse neurofibrillary tangles, and calcification of the Fahr type, however, the clilical features of this new entity are not known in the description of detail. We report a patient with atypical presenile dementia which appeared to be consistant with that entity, together with the results of a comprehensive neuropsychological and neuroradiological examination. The patient was a 65-year-old right-handed housewife. At about 58 years of age, she started to lose spontaneity and develop a mild memory disturbance. At age 61 she transiently, experienced hallucinations and delusions. During the subsequent 8 years there was a very slight decline in global intellectual efficiency. In addition, she showed slow but definite progression of language disturbances characterized by anomia and loss of ability to grasp the meaning of words, particularly abstract nouns. She performed poorly on tasks with good sensitivity for detecting frontal lobe dysfunction, such as the Wisconsin Card Sorting Test and the hand sequence test. All other cognitive functions appeared to be relatively well preserved, however moderate dyscalculia was present. There was no socially inappropriate or stereotyped behavior, but the patient lost insight into her disease. The patient's activities of daily living on the ward were self-maintained. An EEG was normal. CT and MRI scans showed circumscribed bilateral fronto-temporal atrophy and bilateral mineralization in the basal ganglia and cerebellar white matter.(ABSTRACT TRUNCATED AT 250 WORDS)