Normal or mild hearing impaired persons sometimes express their hearing acuity worse than their true hearing levels for the purpose of benefit and compensation. For examples, persons who want to avoid the duty of military service, traffic accident patients and industrially traumatized patients have possibilities of malingering. Authors performed pure tone audiometry, Békésy audiometry, impedance audiometry and BERA in 110 patients who visited Yonsei Medical Center from Jan. 1983 to Jan. 1984 for medical certificates. Unreliable patients were 35 cases(31.8%) and they showed abnormal findin the following orders : 1) Unreliable Békésy form, 2) Discrepancy between the pure tone and Békésy threshold, 3) Pure tone variability, 4) Impedance audiometry, 5) Air conduction interaural attenuation greater than normal range, 6) Bone conduction interaural attenuation greater than normal range. From the analysis of above data, as a single test, Békésy audiometry was most useful, but in many occasions, combination of all of the above tests were necessary to decide the reliability of the test results.