We report a 65-year-old man with parkinsonism, supranuclear gaze palsy, and dementia. The patient was well until 58 years of the age (1984) when he noted an onset of tremor in his right hand. He visited our neurology service two years after the onset; neurologic examination at that time revealed moderate restriction in down ward gaze, horizontal gaze nystagmus in left and right gaze, stooped posture with loss of arm swing when he walked, slight rigidity in the neck and the right upper and lower extremities, and resting tremor in his right hand and foot; mentation was intact. He was treated with 600 mg of levodopa with carbidopa; his tremor partially improved. He received left Vim thalamotomy on March 14 of 1987. His tremor disappeared after the thalamotomy. Post-operative course was complicated by transient clouding of consciousness due to subdural hematoma which developed after the surgery. Six months after the surgery, he noted increase in the unsteadiness of gait; he also experienced urinary incontinence once in a while, and he became mentally dull. In November of 1988, he had episodes of stiffening of his body. Although his spontaneous speech was very much reduced, he repeatedly hummed a same tune; no one could make him stop humming. In June of 1989, he was totally unable to move his eyes in the vertical direction. He was hospitalized to another hospital in May of 1990 where he died six month after admission because of pneumonia. The clinical course of this patient was characterized by the onset with parkinsonian resting tremor, and supranuclear gaze palsy and dementia in the later course. The patient was discussed in a neurological CPC and the chief discussant arrived at the conclusion that the patient had an overlap syndrome of progressive supranuclear palsy (PSP) and diffuse Lewy body disease. Majority of the participants thought that the patient had progressive supranuclear palsy, but many of them had an impression that parkinsonian tremor responding to levodopa as the initial symptom for PSP is rather unusual. Postmortem examination revealed severe loss of neurons in the substantia nigra, the globus pallidus, and the subthalamic nucleus with reactive gliosis; formy spheroids were seen in the substantia nigra, however, no Lewy bodies or neurofibrillary tangles were observed. Moderate neuronal loss was also seen in the dentate nucleus of the cerebellum. In addition, the precentral gyrus showed moderate neuronal loss, astrocytosis, and spongy change in the second layer; ballooned neurons were seen in the third and the fifth layers. Histologic characteristics were consistent with the pathologic diagnosis of corticobasal degeneration.