Neuropsychological symptoms were studied in 9 cases of presenile dementia suspected of Alzheimer's disease. The patients were diagnosed according to their clinical symptoms, CT-scans and EEGs. (1) Major clinical symptoms included memory disturbance (9 cases), visuo-spatial agnosia (8 cases), constructional apraxia (7 cases), and difficulty in the use of implements (5 cases). (2) In symptoms of visuo-spatial agnosia, disorders of spatial perception and loss of topographical memory were frequent; however, no unilateral visual neglect was observed. (3) Ideomotor apraxia (1 case) and ideational apraxia (2 cases) were observed. Five cases showed difficulty or clumsiness in the use of implements, such as gas or oil heaters, telephones, cultivators, etc. (4) Eight cases showed fluent speech and mild word amnesia. They also showed mild disturbance in language comprehension, especially in word meaning comprehension. Writing to dictation in Kanji characters was more impaired than that in Kana syllabary. (5) From CT-scan studies, the relationship between the location of prominent cerebral atrophy and the neuropsychological symptoms was investigated.