Two hundred thirty patients with cysticercosis were reviewed. Investigation with CT scan has led to a more detailed understanding of the natural history of human infestation which is essential to the evaluation of new pharmacological and neurosurgical treatments. In contrast to reports emphasizing the need to extirpate all intraventricular cysts, many of our patients needed only ventricular shunt implantation. The ability to evaluate and reevaluate hydrocephalus by CT scan permitted comfortable use of ventricular shunt insertion as the only treatment. Nevertheless, cysts in the fourth ventricle should nearly always be extirpated, because these cysts, by their mass effect, may cause herniation even after shunt implantation. Serious morbidity and death occur chiefly in patients who develop hydrocephalus from intraventricular and basilar infestation. It is unlikely that praziquantel will be effective in patients who present with symptoms of hydrocephalus.