We have analyzed traces of vergence eye movements while subjects watch three-dimensional (3D) and two dimensional (2D) movies, and found that 2D images without binocular disparity sometimes evoked convergence similar to those found in the 3D condition. In this study, we investigated factors that drove convergence other than binocular disparity. As previously presented, 3D/2D movies were projected on an 80 inch-screen in a dark room (10 lux) by two liquid crystalline projectors with/without polarized filters to provide binocular disparity, field-sequentially. To monitor the gaze of the subject, we measured binocular eye movements and head movements with a new binocular video oculography (Newopto) and a magnetic motion sensor (Polhemus). A 2D movie representing driver's view of a go-cart (160 sec), which included forward scenes and expanding optic flows, was shown to fifteen subjects. The motion vectors localized to their gaze points were calculated, and the optic flow was estimated based on flame-by-flame analyses of images. The traces of vergence eye movements consisted with the changes in the optic flow. It is suggested that most of factors that drove convergence in 2D movies are closely related to optic flow. <b>[J Physiol Sci. 2006;56 Suppl:S92]</b>