Effects of optical transposition created by up-down reversing goggles and left-right reversing goggles were investigated on two locomotory tasks, i.e., walking along a corridor and going up and down stairs. ~ In experiment I, the subjects' own predictions about the relative difficulty between the two visually transposed conditions, were recorded, where mast subjects predicted that it would be more difficult to walk in the up-down reversed condition than to walk in the left-right reversed condition. The statements of the subjects after having completed the tasks, however, showed the oposite results from the predictions they made. Majority of the subjects were not able to complete the experimental trials under the left-right reversed condition because of their intolerable feeling of nausea. The results of experiment II which used the three-way ANOVA confirmed the results of experiment I and showed marked practice effects in the left-right reversed condition.