brief history of the advances made in acoustic tumor diagnosis and treatment is presented indicating the benefits derived therefrom over the past 15 years. The recent application of brain stem electric response audiometry (BERA) as related to tumors affecting the auditory nerve is reviewed. Patients were considered to have a positive test result for tumor detection (abnormal BER) when their responses showed one of three characteristics: 1. wave V latencies were significantly different from the normal mean, 2. the interaural latency difference (ILD) was greater than .3 msec. (.4 msecs when the hearing loss was greater than 65 db HL), or 3. no response could be recognized at suprathreshold levels. An abnormal BER result was observed in 92.6% of 27 surgically proven tumors in this study. Two patients with surgically proven tumors had a false-negative test. In a series of 115 nontumor patients with asymmetric sensorineural hearing losses of multiple etiology, one in three had an abnormal BER result. All conductive losses increased wave V latency values. The authors have concluded that an abnormal ILD is far from pathogmonic for a tumor affecting the auditory nerve; interpretive caution is recommended with even small conductive hearing losses. False-negative responses are few, false-positive responses are common (relative to tumor diagnosis). BERA is the most efficient audiometric test available today in our search for tumors affecting the auditory nerve. As such, this test probably heralds a new era in diagnostic audiology.