Three theories have been suggested as to the cause of space motion sickness: 1)eye and vestibular sensory mismatch, 2)abnormal shift of body fluids producing increased intracranial pressure and 3)prewarning signals for unpleasant physical situations by self-produced neurotoxic substances released in the body. We are interested in the possible functional disabilities⁄incongruities of eye, head and body movements in 0-G. Space motion sickness might be explained from the viewpoint of lack of coordination of the movements of the eye and head. It is important to ascertain the significance of gravity in the maintenance of human visual stability. We will examine the coordination of Japanese Payload Specialist (JPS) eye and head movement by electrooculogram and neck muscle electromyogram recordings, as well as obtaining a subjective evaluation of visual stability from the PS during space flight. We hypothesize that 1)poor performance of the eye movement will be observed, 2)unusual neck muscle activity will be observed and 3)there will be decreased visual stability in micro gravity. We obtained all digital data and VCR taped image data in