Caloric test is one of the most useful procedure in evaluation of vestibular function. Nystagmic threshold was originally measured by controlling water temperature without unpleasant sensation. Recently, by development of the ENG apparatus the minimal nystagmus can be detected more precisely. In the present study it was aimed to pursue the possibility of measurement of the nystagmic threshold of caloric test in 42 young adult by employing microthermoregulating system that can control exact water temperature up to 0.1℃. Subjects were chosen from healthy Korean between the age from 16 to 27(mean age 24.0). They had no history of physical or mental abnormality, hearing impairment, dizziness. Those who had a history of middle and external ear diseases were precluded. The results obtained were as follows. 1. Thresholds to the cold and warm water in both sexs were : The stastistical significance between sexes was shown in the left ear to cold water(p<0.05), and right ear to hot water(p<0.01). Man : 1) left ear to cold water 33.79±0.59℃, 2) left ear to hot water 40.61±0.81℃, 3) right ear to cold water 33.86±0.48℃, 4) right ear to hot water 40.72±0.69℃, Woman : 1) left ear to cold water 34.28±0.69℃, 2) left ear to hot water 40.15±0.47℃, 3) right ear to cold water 34.10±0.58℃, 4) right ear to hot water 40.10±0.31℃ 2. Average threshold of total 42 normal subjects were ; Left ear to cold water 33.92±0.65℃, right ear to cold water 33.92±0.52℃, left ear to hot water 40.48±0.75℃, right ear to hot water 40.55±0.66℃. There was no stastiscal significance between left and right. 3. The latency in the case of cold water was 59.23±a2/1.68 sec. and in the hot water was 59.36±1.94℃. 4. As unplesasant symptom manifested during caloric test, mild nausea in 4 cases(9.5%) was evident. 5. Based on the these results, it is concluded that the threshold of nystagmus is accurately able to be estimated by employing the microthermoregulating device. Thus, it is considered that the caloric test can be safely performed with few side effectly using these facilities.