Two different binocular cues are known for detecting motion in depth. One is disparity change in time and the other is inter-ocular velocity difference. Shioiri, Saisho and Yaguchi (1999) demon-strated that motion in depth can be seen based solely on inter-ocular velocity differences as well as on the disparity change in time. They used conditions in which either cue was minimized and measured performance based on motion in depth, finding better performance than chance level when either velocity cue or the disparity cue was almost isolated. However, there may have been influences from the cue minimized in each condition, since it was practically impossible to isolate perfectly either cue. I re-analyzed their data to examine whether the performance in the condition with disparity change and that in the condition with inter-ocular velocity difference were correlated. The result showed the correlation is very low and therefore, we can conclude that the visual system has two different mechanisms for motion in depth.