We dissected 30 human temporal bones in order to establish a reliable method for avoidance of the membranous labyrinth in acoustic neuroma surgery. We believe that the variability of the surgical landmarks is sufficient to make complete reliance on anatomic measurements quite treacherous. Fine-cut computed tomograms were evaluated, and it was determined that measurements taken from such scans can define the anatomy of individual temporal bones. We conclude that hearing conservation surgery for acoustic neuroma is a relatively difficult surgical exercise and that complete familiarity with the anatomy and use of all available landmarks is required for successful tumor removal and hearing conservation. Success can be improved further by using measurements taken from the individual patient's preoperative CT scan.