Three children with cerebral oligodendrogliomas causing partial complex or generalized seizures presented with completely normal neurologic examinations. CT showed low-density, nonenhancing surface lesions. Although these CT features are usually associated with infarcts or cysts, neoplasm was suspected because of irregularity of the margins and erosion of the adjacent inner table of the skull. Oligodendrogliomas often enlarge slowly and may cause seizures years before they produce focal neurologic signs. CT of all children with seizures not responsive to anticonvulsant medication and focal clinical or EEG abnormalities will hasten diagnosis of slowly growing intracranial mass lesions.