Cranial computed tomography (CCT) has already been demonstrated to provide significant diagnostic information in patients with neurologic disease and to reduce the need for special neuroradiologic procedures. The important question remaining is: Should CCT replace the radionuclide brain scan (RBS) as the first diagnostic study in most patients with suspected intracranial pathology? Data are now available to define the costs and benefits of this substitution. The technical costs of CCT have been determined by a national survey and have shown to be $130 per patient at a volume of 50 patients per week. The costs of RBS at the Mallinckrodt Institute have been estimated at $51 per patient. Data from the literature indicate that CCT is slightly more sensitive and considerably more accurate than RBS. Eighteen to twenty-eight percent of patients studied by CCT and RBS have abnormalities (e.g. cerebral atrophy and ventricular dilatation) that are only detected by CCT, and the overall accuracy of CCT is 95%, while the accuracy of RBS is approximately 70%. Substituting CCT for RBS is cost-beneficial. Although CCT is more costly, it increases overall accuracy by approximately 25%. The cost benefit is further increased by the reduction of complicated diagnostic procedures (and associated hospitalization and morbidity) and improvement in diagnostic information for the individual patient. Substituting CCT for RBS may not be more costly because a positive RBS will be followed by CCT (because of increased diagnostic information), and a negative RBS may be followed by CCT (because of increased accuracy), whereas a positive or negative CCT is unlikely to be followed by RBS.