Seventy patients suspected clinically of having an acoustic tumor were evaluated using the computed tomographic (CT) scan as the initial neuroradiological procedure, followed by CO2 contrast CT cisternography in cases where the intravenous contrast-enhanced scan did not reveal any lesion. Forty-eight gas CT cisternograms revealed 10 small acoustic tumors, 2 of which were totally intracanalicular. The authors present a review of the basic CT anatomy of the temporal bone as it relates to acoustic tumors. Based upon the ease of performance of the procedure, the low postexamination morbidity, and the excellent diagnostic results, CO2 CT cisternography is recommended as the procedure of choice in the diagnosis of small and intracanalicular acoustic tumors.