The visual and vestibular signals interact synergistically to stabilize gaze during natural head movement. In the Optokinetic system, two visual pathways transport the visual signal to the vestibular nuclei. When optokinetic stimuli are stopped suddenly in a dark room, after nystagmus(OKAN and reversed OKAN) will be generated in mammals. In case of bilateral vestibular loss, optokinetic after nystagmus was disappears in animals, but David Zee showed that initial reversed OKAN could be observed in man⁴¹⁾. We investigated the meaning of OKAN and reversed OKAN response in bilateral vestibular loss humansubjects. Normal adult(n=5) and bilateral vestibular loss patients(n=4) were included in this study. After optokinetic stimuli(40deg/sec, 2.56 traget space, 60sec), eye movement was recorded for 20 sec in a dark room. SPV(slow phase velocity) was checked during right and left direction of visual stimuli for 20sec. The bilateral vestibular loss was defined as the sum of peak warm SPV of eye movement and peak cool SPV in bithermal caloric test, and we confirmed it with 4 degrees ice water irrigation and sinusoidal rotation test. The results were as follows. 1) OKAN asymmetry was not seen in normal and bilateral vestibular loss subjects. 2) OKAN was always observed in normal adults but not always in bilateral vestibular loss subjects. 3) Reversed OKAN that follows the OKAN was noted in 2 cases of normal adults. But the initial reversed OKAN was seen in 2 cases from the bilateral vestibular loss.