Thirty-seven patients with 39 acoustic neurinomas were studied with computed tomography (CT). Six tumors (15%) were seen on the nonenhanced scans and infusion of contrast material demonstrated 23 more tumors. Ten tumors (26%) were not seen as soft-tissue masses on the enhanced CT scans. However, these same 10 cases yielded 4 ipsilateral abnormal internal auditory canals when viewed with a bone window. Findings suggestive of acoustic neurinomas were found in 85% of proven sites. Important factors in the CT diagnosis of acoustic neurinomas are good-quality, motion-free scans, contrast enhancement and analysis of bone detail.