When some items in a menu are selected more frequently than others, as is often the case, designers or individual users may be able to speed performance and improve satisfaction by placing several high-frequency items at the top of the menu. Design guidelines for split menus were developed and applied. Split menus were implemented and tested in two field studies and a controlled experiment. In the field study conditions performance times were reduced from 17 or 58% depending on the site and menus. In the controlled experiment split menus were significantly faster than alphabetic menus and yielded significantly higher subjective preferences. A possible resolution to the continuing debate among cognitive theorists about predicting menu selection times is offered. We conjecture and offer evidence that the logarithmic model applies to familiar (high-frequency) items and the linear model applies to unfamiliar (low-frequency) items. (Also cross-referenced as CAR-TR-649) ACM Transactions on Computer-Human Interaction, vol. 1, #1 (March 1994) 27-51 %I Human Computer Interaction Laboratory