We report a 74-year-old woman with parkinsonism and dementia, who died 4 years after the onset of the disease. She was well until 70 years of the age (1993) when she noted slowness in the movement in her left hand. She also developed gait disturbance and the similar symptoms spread to the right upper and lower extremities. Two years after the onset, she had difficulty in walk, and was admitted to our hospital on March 9, 1995. Her daughter had the onset of hand tremor at 50 years of the age and gait disturbance at 52. Her gait improved after levodopa treatment, but her MRI revealed a liner T2-high signal lesion along the outer surface of each putamen. On admission, the patient was alert but slighted demented. Higher cerebral functions were normal. She had a masked face and small voice. Her gait was of small step without arm swing. Retropulsion was present. Rigidity was noted in the neck but not in the limbs. She was bradykinetic but tremor was absent. She was treated with levodopa/carbidopa, dops, and bromocriptine with considerable improvement and was discharged on March 30, 1995. On January 19, 1996, she developed fever and hallucination; she became more akinetic and admitted again. She showed marked dementia and stage IV parkinsonism. She was treated by supportive measures with improvement in the general condition, but she was found to have a gastric cancer for which a subtotal gastrectomy was performed on March 11, 1996. Post-operative course was uneventful, but her parkinsonism progressed to stage V. She was transferred to another hospital on May 13, 1996. In July 21, 1996, she developed dyspnea and fever and was admitted to our hospital again. She was somnolent. Rigidity was moderate to marked and she was unable to stand or walk. By supportive cares, her general condition improved and was discharged to home on November 4, 1996. She developed fever on June 13, 1997 and admitted to our service again. Her BP was 150/90 mmHg. She was alert but markedly demented. Laboratory examination revealed increases in liver enzymes (GOT 75 IU/l, GPT 101 IU/l) and renal dysfunction (BUN 68 mg/dl, creatinine 3.27 mg/dl). Subsequent hospital course was complicated by renal failure and thrombocytopenia (33,000/ml). She expired on July 1, 1997. The patient was discussed in a neurologic CPC, and a chief discussant arrived at the conclusion that the patient had diffuse Lewy body disease and her daughter striatonigral degeneration. Some participants thought both the patient and her daughter had diffuse Lewy body disease. Post-mortem examination revealed marked degeneration of the substania nigra and the locus coeruleus. The medial part of the nigra also showed marked cell loss. Lewy bodies were found in the remaining nigral and coeruleus neurons. Cortical Lewy bodies were very few and the striatum was intact. Pathologic diagnosis was Parkinson's disease. Dementia was in part attributed to the marked degeneration of the medial part of the substantia nigra.