We report a 64-year-old man with parkinsonism as an initial symptom, which was followed by dementia and abnormal behaviours. He was well until 1985, when he was 49 years old, when he noted rest tremor in his right hand. Soon tremor appeared in his left hand as well. He was seen in our clinic and levodopa was prescribed. He was doing well with this medication, however, in 1993, he started to suffer from on-off phenomenon. He also noted visual hallucination. In 1994, he stole a watermelon and ate it in the shop. He repeated such abnormal behaviours. In 1995, he was admitted to the neurology service of Hatsuishi Hospital. On admission, he was alert and oriented. He did not seem to be demented; however, he admitted stealing and hypersexual behaviours. No aphasia, apraxia, or agnosia was noted. In the cranial nerves, downward gaze was markedly restricted. He showed masked and seborrhoic face, and small voice. No motor palsy was noted, but he walked in small steps with freezing and start hesitation. Marked neck and axial rigidity was noted. Tremor was absent except for in the tongue. No cerebellar ataxia was noted. Deep tendon reflexes were diminished. Plantar response was extensor bilaterally. Forced grasp was noted also bilaterally. He was treated with levodopa and pergolide, but he continued to show on-off phenomenon. His balance problem and akinesia became progressively worse; still he showed hypersexual behaviour problems. He also showed progressive decline in cognitive functions. In 1997, he started to show dysphagia. He developed aspiration pneumonia in July of 1998. In 1999, he developed emotional incontinence and became unable to walk. He also developed repeated aspiration pneumonia. He died on March 1, 2000. He was discussed in a neurological CPC and the chief discussant arrived at a conclusion that the patient had corticobasal degeneration. Other diagnoses entertained included dementia with Lewy bodies, diffuse Lewy body disease, and frontotemporal dementia. Majority of the participants thought that diffuse Lewy body disease was most likely. Post-mortem examination revealed marked nigral neuronal loss, gliosis and Lewy bodies in the remaining neurons. Abundant Lewy bodies of cortical type were seen wide spread in the cortical areas, but particularly many in the amygdaloid nucleus. Lewy bodies were also seen in the subcortical structures such as the dorsal motor nucleus, oculomotor nucleus, Meynert nucleus, putamen, and thalamus. What was interesting was marked neuronal loss of the pontine nuclei, demyelination of the pontocerebellar fiber, and moderate neuronal loss of the cerebellar Purkinje neurons, a reminiscent of pontocerebellar atrophy. However, the inferior olivary nucleus was intact.