THE PURPOSE of a classification is to allow surgeons operating on a particular lesion to evaluate and compare their results while speaking within a framework common to all. Such a classification is necessary when speaking about acoustic neuromas because today these tumors are being diagnosed and surgically treated in every stage of their clinical development. There is no question that the diagnosis of acoustic neuroma is being made today in greater frequency than ever before. All patients presenting themselves with unilateral hearing loss, tinnitus, and unsteadiness are suspect, whereas in years past this diagnosis was not entertained until the patient developed involvement of multiple cranial nerves and in some cases elevated intracranial pressure. With the early recognition of these tumors, in addition to the rather obvious appreciation of those tumors that have progressed to late stages, we are now confronted with a lesion that presents itself to the clinician and