A cooperative study by five university centers assessed the relative usefulness of computed tomography (CT) of the head and compared with with plain head radiography, radionuclide brain scanning, and neuroangiography for the detection and diagnosis of masses in the brain. CT with and without contrast enhancement was the most accurate neurodiagnostic method employed in 2,928 patients, 1,071 of whom were found to harbor intracranial tumors. Angiography was as accurate as CT, whereas radionuclide studies and plain radiography were much less accurate and were seldom found to be positive if CT and angiography were negative.