Cerebral cysticercosis, is unfortunately, a frequent disease in Korea. Cysticercosis in man is exclusively due to the development of Taenia solium larvae, called Cysticercus cellulosae, which is a frequent parasite in the pig. The clinical symptoms which are varied and similar to those of any other tumor of the brain, are depent on the location, number of parasite, intensity of infestation and susceptibility of the host. The headache, vertigo, nausea and vomiting, appearing periodically, and chiefly after a rapid change in the position of the head, were indicative of a cysticercus lying free in the fourth ventricle. We have recently experienced a case of cerebral cysticercosis which involved the 4th ventricle. A forty-year-old man was aditted to the Department of Neurosurgery, College of Medicine, Korea University in June, 1978 because of severe headache, repeated vomiting and diplopia which progressed gradually for two months previous to admission. On admission, there were no specific localizing and lateralizing neurological abnormalities except for signs of mild cerebellar dysfunction and signs of increased intracranial pressure accompanying with bilateral optic papilledema. Conray ventriculogram disclosed the dilation of proximal portion of the 4 th ventricle and smoothly rounded central filling defect of the 4 th ventricle. Brain C-T Scan demonstrated the marked dilation of 4 th ventricle in found shape without evidence of midline shift or compression. This enlarged 4 th ventricle with water density was shown no evidence of the contrast enhancement. Suboccipital craniectomy was performed and a cystic mass was removed from the fourth ventricle. Pathological diagnosis of the specimen was cysticercosis. Following surgery, the patient's symptoms cleared up and neurological deficits and papilledema improved gradually.