A new view of mental rotation in humans is presented. Rather than being a perceptual phenomenon, mental rotation of objects is supposed to be an imagined action in the sense that its only difference to real action is the absence of motor output. A series of experiments is reported which shows that the difference in speed between mental and manual rotation are negligible and that performing rotational hand movements interferes with mental rotation and vice versa. It also could be shown that the preparation of rotational hand movements is already sufficient to infl-ence mental rotation. The general role of motor processing in dynamic visual imagery is discussed, considering the underlying neurophysiology.