Introduction The diagnosis of an acoustic neuroma while still within the confines of the internal auditory canal is no longer only of academic importance. Early diagnosis can be followed by removal of the tumor through a translabyrinthine or middle fossa approach, before it has involved vital structures in the cerebellopontine angle. X-rays of the petrous pyramid made with proper equipment, correct positions, and the correct exposure constitute a very important part of the diagnostic work-up of patients suspected of having tumors of the internal auditory canal. Eighty-five per cent of 54 proven cases of acoustic neuromas had positive x-ray findings. The purpose of this paper is to review the radiographic techniques used in the diagnosis of lesions of the internal auditory canal. Normal Anatomy Camp and Cilley,1 in their study of normal differences in diameters of the internal auditory canals, conclude that variations in diameter of the canals between