Caloric test is an essential step in evaluating a dizzy patients but the results may be variable by the different examiners or even when the test is performed in same manner by same examiner on the different days mainly due to the different visual condition and mental activity. This apparent inconsistency of response detracts greatly from the clinical usefulness of caloric test. It is well known that vestibular nystagmus is inhibited by the visual fixation and Frenzel glasses are widely used to evoke nystagmus by eliminating visual fixation in the clinic. Recently visual fixation was examined by measuring and comparing the slow velocity of caloric nystagmus in darkness and in light and it was observed that visual fixation suppress vestibular nystagmus via cerebellum in animal. We have obtained the normal value of visual suppression in normal adult subjects and observed that visual suppression was reduced in the lesion of cerebellum, parietal lobe and brainstem. The results were as follows ; 1) Visual suppression of the slow phase velocity of caloric nystagmus was 41.5±10.6% in 30 normal adults, aged from 21 to 29 years. There is no significant difference between male(43.4±9.8%) and female(39.7±11.0%) also between right(40.2±10.2) and left(42.7±10.8%). 2) Visual suppression of caloric nystagmus toward the side of lesion was more reduced than toward the contralateral side in unilateral lesion of cerebellum, parietal lobe and brainstem. Visual suppression was -33% & 0% in cerebellar lesion and 15% in parietal lobe lesion and 0% in brainstem lesion. We concluded it in consideration of the above result that visual suppression test is very useful in differential diagnosis of cerebellar lesion, brainstem lesion and parietal lobe lesion.