Work on the commercial development of a 70mm, 15-perforation motion-picture projector has resulted in the production of four prototype mechanisms. One of these, installed in the Fuji Pavilion at Expo '70, employs a 25,000-W xenon short-arc lamp to project a 15-min, multiple-image motion picture on a screen measuring 43 by 62 ft. One of the difficult technical problems that had to be solved was how to advance the film at 15 perforations/frame, 24 frames/s, with a pulldown time of less than 10 ms, while simultaneously achieving good registration, good film life and mechanical reliability. Possibilities of excessive accelerations and impact forces on the film were matters of concern. The solutions, obtained from mathematical analyses and observations of prototype operation, involved appropriate film-guide design, the use of air jets to assist in forming and picking up the loops, and the incorporation of a mechanical device for producing controlled and accurate registration without perforation damage. A description is given of the behavior of the film as the rolling loop forms, grows, moves toward the gate where the registration takes place, shrinks and finally disappears.