Background: Ependymomas usually arise from the ventricular surface. Methods: We report an 11-year-old female who presented with a supratentorial ectopic ependymoma. Results: The patient presented with a two-month-history of progressive headache, nausea and vomiting. Examination revealed papilledema, horizontal nystagmus, diplopia on upward gaze, and right pronator drift. CT scan showed an enhancing left precentral subcortical lesion measuring 3 cm in diameter with associated edema and mass effect. Its medial border was located 3 cm from the ependymal surface of the ventricle. A firm tumour was dissected from the centrum semiovale white matter, and removed in toto as confirmed on MRI. Pathological examination revealed histological, immuno-histochemical and electron microscopic features consistent with an ependymoma. Spine MRI and bone marrow aspirate, as well as lumbar puncture of cytology failed to show any dissemination. Conclusion: From the literature review, this represents an exceptional ependymoma located at the distance from the ventricular system or cisterns. Different pathogenic alternatives are discussed. RESUME: Ependymome ectopique supratentoriel. Objectif: Les 6pendymomes sont gdn^ralement issus de la surface ventriculaire. Methode: Nous rapportons d'une fillette de 11 ans prSsentant un Ependymome supratentoriel ectopique. Resultats: Cette patiente souffrait depuis 2 mois de c6phal6es progressives, de nause'es et de vomissements. A l'examen neurologique, on relevait un oedeme papillaire, un nystagmus horizontal, une diplopie pour le regard vers le haut et une pronation de la main droite a l'epreuve des bras tendus. Le CT scan montrait une lesion de 3 cms de diametre, sous-corticale, pr6centrale, captant le contraste, entourfie d'oedeme avec effet de masse. Sa partie m&liane 6tait situ6e a 3 cms du ventricule. Cette tumeur ferme a et6 totalement extirpde du centre semi-ovale tel que confirme a 1'IRM post-op6ratoire. Le diagnostic retenu aprfes examen histologique, immuno-histochimique et apr&s microscopie electronique fut celui d'6pendymome. Une IRM spinale, un examen de moelle osseuse et une ponction lombaire n'ont pas montre de dissemination tumorale. Conclusion: Aprfes revue de la literature, ce cas paratt exceptionnel par sa localisation a distance du systeme ventriculaire ou cisternal. Differentes alternatives pathogfiniques sont discut&s.Can. J. Neurol. Sci. 1995; 22: 316-319 Ependymomas are rare tumours arising from the cells lining the ventricular system and the central canal of the spinal cord. They account for 1.2% to 6% of primary intracranial neoplasms 1 " 4 and 24% of the intraspinal tumours. 5 Intracranial ependymomas are preferentially encountered in children in whom they represent up to 12% of all brain tumours, 3 -5 " 9 whereas intraspinal ependymomas occur essentially in young adults. 2 -5 -10 -" Approximately two-thirds of cerebral ependymomas are infratentorial and most of them arise within the fourth ventricle. '-4 "" We present the unusual case of supratentorial epe...