Fisher's syndrome was studied in six patients, one of whom was an 11-year-old girl, and the nosological position of this neuro-ophthalmological disorder was reviewed. The clinical features of the ophthalmoplegia in these cases were reported as secondary to a transient inflammatory lesion in the mid-brain; this was demonstrated in one of the cases by an enhancing area on CT scan. This mid-brain localization could explain not only the classical Fisher's triad but also many variations of the syndrome. The overlap of our cases of Fisher's syndrome with so-called brain-stem encephalitis of Bickerstaff has been emphasized. Many cases of Fisher's syndrome could therefore correspond to an inflammatory process at brain-stem level with or without nerve-root involvement. Clinical and neurophysiological findings show, however, that there is peripheral damage in some cases, so that a neutral attitude needs to be maintained on the nosological position of Fisher's syndrome.