Acoustic neuroma was first reported by Sandifort in Deutch on 1777. Most patients with acoustic neuroma first present to the otologist with the chief complaints of unilateral progressive hearing loss, tinnitus and dizziness. In the past, small tumors were difficult to detect, so the surgical removal was done after notifing of general CNS symptoms. Armed with advanced methods of early diagnosis more accurate and sensitive audiometric, vestibular and radiologic methods of investigation which are able to detect small tumor, modern anatomic approaches and microsurgical techniques, the otologist is able to reduce the operative morbidity and mortality to levels never known before. But the improved result with surgery could not have been possible without teamwork, so close cooperation with the diagnostic services, and with a team consisting of a otologist, neurosurgeon, anesthetist, is essential. However the most important role in early diagnosis still remained with the clinician. In our hospital, 1% of patients who visited to our OPD were complained of unilateral progressive hearing loss, and among them, we suspected of acoustic neuroma in 19%. So the author studies 26 cases of acoustic neuroma who confirmed surgery in our hospital during 10 years for the study of clinical features and histopathology and progression, and the result were reported as followings : 1) Male to female ratio was 1.4 to 1. The most frequent age incidence was fourth decade. 2) Right to left ratio was 1 to 1. Size distribution was followed small (less than 1.5cm) ; 2 cases (8%), medium (1.5cm to 3.0cm) ; 8 cases (31%), large (more than 3.0cm) ; 16 cases (62%). 3) On admission, the most common complaint was hearing loss, then dizziness, headache and tinnitus were followed. 4) The duration of symptom was various, but the mean was 30 months. 5) The most common involved cranial nerve was 8th nerve, then 5th, 9th, 10th, 7th and 6th nerve were followed. 6) Average protein content in CSF was about 123.4mg% and increased in 68% patients. 7) In histopathology, type A was 15 cases (58%), type B was 6 cases (23%) and mixed type was 5 cases (19%). 8) Caloric test result was followed hypoactive ; 2 cases (11%), no response ; 16 cases (89%). 9) Audiologic test result was followed, A. PTA : mild hearing loss ; 1 case (7%), moderate severe hearing loss ; 1 case (7%), severe hearing loss ; 3 cases (20%), deaf ; 10 cases (67%). B. Tone decay test was taken in 4 patients and 3 patients had positive result. C. SISI test was taken in 3 patients, and the result was more than 80% in all patients. D. Bekesy audiogram was taken in 3 patients, and the result was type III in all patients. E. Impedance audiogram was taken in 4 patients, and the result was absence of reflex in all cases. 10) Radiologic positive result was followed, Plain X-ray ; 18/25 (72%), Tomogram ; 4/4 (100%), Angiogram ; 22/25 (89%), Posterior fossa myelogram ; 1/1 (100%), C-T scan ; 11/11 (100%).