Objective: To report the clinical and neuropathological features in a patient with Creutzfeldt-Jakob disease with amyotrophy and demyelinating polyneuropathy. Design: Case report. Patient and Results: A 62-year-old man had progressive numbness of the left foot, unsteady gait, diminished deep reflexes, fasciculations, and tactile hypesthesia on the feet. Cerebrospinal fluid, electroneurography, and electromyography were suggestive of chronic inflammatory demyelinating polyneuropathy. He was treated with plasmapheresis, corticosteroids, and immunglobulins, with minimal improvement. After 2 months, severe amyotrophy, polyneuropathy, cerebellar signs, and dementia developed, and he died 8 months after onset of the disease. Autopsy and prion protein immunohistochemistry proved typical Creutzfeldt-Jakob disease. No mutation was found in the prion protein gene, and the codon 129 polymorphism was methionine-valine. in the ventral horn, the loss of the motoneurons was accompanied by prion protein immunoreactivity. The peripheral nerves were segmentally demyelinated but free of prion protein deposition. Conclusions: The view that peripheral neuropathy and amyotrophy may occasionally be an integral part of Creutzfeldt-Jakob disease is supported by our case, which showed these-abnormalities simultaneously. These symptoms, when prominent, may cause problems in differential diagnosis.