We can have knowledges about degree of hearing impairment and type of hearing impairment through various audiologic tests. Among them tuning fork tests are the most basic and clinically useful. The Rinne, the Weber and the Bing test are most widely used for the clinical purpose. But there are surprisingly few reports about tuning fork tests as an adjunctive measure in the diagnosis of the hearing loss. So we evaluate the results of three standard tuning fork tests - the Rinne, the Weber and the Bing - at frequencies of 256, 512 and 1,024Hz as a double blind prospective study of 106 normal persons, 79 patients with air-bone gap and 59 sensorineural hearing loss patients. The conclusions drawn from this study are : 1) The differential diagnosis of conductive hearing loss and sensorineural hearing loss, the more reliable tuning fork test was in order of the Rinne, the Weber and the Bing test. 2) The most reliable frequency of the tuning fork test, the Bing test was 256 Hz, 512 Hz and 1,024Hz, the Weber test was 512Hz and 1,024 Hz and the Rinne test was 256Hz tuning fork. 3) The relation of the degree of the hearing loss and tuning fork test, when the air-bone gap was at least 20dB or more, the Bing and the Rinne test was valid and reliable but the Weber test was reliable when the different degree of the hearing loss of the both ear was at lest 10dB or more. 4) Generally the finding of these tuning fork tests compare with pure tone audiogram was identified. But the reliability obtained with the Bing test at all test frequencies was no clinical value because there are two many false negative response. 5) Tuning fork tests used alone in evaluation of hearing loss are unreliable and without other diagnostic modalities should not be used.