We reported here the quantitative analyses of the language disturbances in mild to moderate dementia of Alzheimer type (DAT) using the Japanese version of Western Aphasia Battery (WAB) and compared these data with those of normal control subjects. Aphasic symptoms were found in 19 out of 20 DAT patients. Sixteen cases were classified into amnesic aphasia and three cases in Wernicke aphasia by WAB criteria. In reading tests, significant differences were found in understanding sentences, Kanji recognition by hearing its structure, and expressing Kanji structure. In writing tests, significant differences were found in the ability to write in dictation and the ability to express ideas by writing. However, the ability to write Kana (Japanese phonogram) was relatively preserved. These results suggest that Japanese DAT patients demonstrate difficulties in writing Kanji letters rather than Kana letters at least in the beginning of the disease.

Key words: dementia of Alzheimer type (DAT), language disturbance, Japanese