We report a 19-year-old girl with multiple sclerosis (MS) who had chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). At the age of 9 (1981), she was diagnosed as having Devic disease, including optic neuritis and transverse myelitis. For two years after the onset of the disease, she suffered from three relapses of MS and was treated with prednisone. At the age of 11, she noticed muscle weakness and sensory disturbance of four limbs. On examination, all tendon reflexes were absent, CSF protein was elevated, and motor nerve conduction velocity of the ulnar nerves was markedly slowed. Sural nerve biopsy showed decreased density of myelinated fibers and de-re-myelinated fibers with onion-bulb formations. Between 11 and 19 years, she had a number of episodes of the central nervous system (CNS) and peripheral nervous system (PNS) deficits with partial or complete recovery by oral administration of prednisone. The clinical course and laboratory data are consistent with MS associated with CIDP. Such our case of MS with CIDP in childhood is very rare. Patients with MS and CIDP may represent a subpopulation who had a common pathogenetic factor for both CNS and PNS demyelination.