Mobile devices with small screens are becoming more common, and will soon be powerful enough to run desktop software. However, the large interfaces of desktop applications do not fit on the small screens. Although there are ways to redesign a UI to fit a smaller area, there are many cases where the only solution is to navigate the large UI with the small screen. The best way to do this, however, is not known. We compared three techniques for using large interfaces on small screens: a panning system similar to what is in current use, a two-level zoom system, and a fisheye view. We tested the techniques with three realistic tasks. We found that people were able to carry out a web navigation task significantly faster with the fisheye view, that the two-level zoom was significantly better for a monitoring task, and that people were slowest with the panning system. Key words: Large interfaces, small screens, mobile devices, screen space, zoom and pan, fisheye views.