The original article was reported by Creutzfeld in 1920, and Jakob in 1921 respectively. CJD is an encephalopathy with worldwide distribution caused by an unidentified unconventional virus. The principal clinical features of CJD are dementia, upper and in some instances, lower motor neuron disorders; basal ganglionic and cerebellar dysfunction; and myoclonus including a heightened startle reaction. The disease is rapidly progressive, leading in several months to stupor, coma, and death. Pathologic changes are widespread, involving the cerebral cortex, basal ganglia, cerebellum, pyramidal tracts, and lower motor neruons of the brain stem and/or spinal cord. This case was 51 years old Korean male, who presented progressive dementia, myoclonus, heightened startle reaction, pyramidal, extrapyramidal symptoms, decerebrated rigidity, and died about 4 months after onset. We diagnosed this case as CJD with typical serial EEG pattern and clinical feature.