Abstract:We present here a case of Klinefelter's syndrome with epileptic psychosis. The patient was a 30‐year‐old male, who suffered from epilepsy for 23 years. He showed auditory hallucination, delusion of reference and delusion of grandeur. At present there are some cases of Klinefelter's syndrome with various psychiatric symptoms, but there are few cases of Klinefelter's syndrome with epileptic psychosis. These various neuropsychiatric symptoms of the present case are thought to be associated with a specific effect of chromosomal abnormality through the cerebral dysfunct