OBJECTIVE Multiple sclerosis (MS) is by far the most popular diagnosis for patients with multifocal neurological disease. Owing to demyelinating inflammatory non-necrotic plaques of the white matter, MS can give remitting symptoms of virtually every part of the central nervous system. Corticosteroids are usually helpful. Devic's neuromyelitis optica (DNMO) is a neurological disease involving only the optic nerves and the spinal cord, where demyelination evolves towards necrosis and atrophy; the prognosis is poor and no satisfactory treatment is known. The objectives of this study are to describe clinical, biological, pathological and radiological data of patients with DNMO and to differentiate DNMO from MS. METHODS We studied the files of 14 patients diagnosed with possible DNMO in three French hospitals between 1980 and 1999 and reviewed the literature. RESULTS Nine patients were included as definite DNMO. Five were excluded because they did not fulfil the diagnostic criteria. For the nine patients with definite DNMO, DNMO was either monophasic or multiphasic. The prognosis was generally poor: two patients died and five others developed severe disability such as blindness, para or quadriplegia or both. Cerebrospinal fluid study and neuroimaging were essential to confirm the diagnosis of DNMO. Various immunosuppressive treatments generally failed to benefit the patients. CONCLUSIONS In the literature (as well as our 14 initial patients) only a few cases of patients described as suffering from DNMO fulfilled the diagnostic criteria. The others showed evidence that another disease like MS was involved. We stress that inclusion and exclusion criteria have to be kept in mind to differentiate clearly DNMO from MS and other central nervous system white matter diseases.