The radiologic investigation of patients with suspected acoustic neurilemmomas may include specialized plain films, thin-section tomography, CT scanning with intravenous contrast enhancement, Pantopaque cisternography, radionuclide scanning, angiography, and pneumoencephalography. Recently we have used intrathecally enhanced (Amipaque)2 CT cisternography tostudy the cerebellopontine angles and fourth ventricle. An assessment is made of the differential diagnostic value and limitations of radiologic modalities both in tumor detection and in accurate localization. A protocol designed to optimize use of the available radiologic modalities is projected from 30 patients with acoustic neurilemmomas.