Tinnitus had been considered as a surgically incurable disease before Dr. Jannetta's microvascular decompression. Fifty-nine patients were operated on between February 1996 and January 1997 in our center. Selection of the patients was based on personal history, neurootologic test and MRI findings. Tinnitogram, audiometry and brain stem auditory evoked potential were evaluated. The anterior inferior cerebellar artery was found compressing the 8th cranial nerve in most patients. Thirty patients were free of tinnitus or more than 75% improved, 21 showed 50-75% improvement, 4 had 25-50%, and 4 have less than 25% improvement or no change. Nine patients who could not hear on the operated side before surgery improved.