User Interface Issues in Mobile Computing James A. Landay and Todd R. Kaufmann Proceedings of the Fourth Workshop on Workstation Operating Systems, Napa, CA, October 14-15 1993, IEEE Computer Society Press, Los Alamitos, CA, 1993, pp 40-47. The age of mobile computing with small portable computers is upon us. However, systems researchers continue to focus on transferring their workstation environments to these machines rather than studying what tasks more typical users wish to perform. Furthermore, we argue that even in the unlikely event that these tasks are the same as those performed by researchers on their workstations, desktop environments and applications may still be inappropriate for the wide range of mobile devices that will be marketed. To explore this area, we have built a mobile computing device along with a user interface system that attempts to address some of these issues.