Human factors contributions to the design of user interfaces are likely to have the greatest impact at early design stages. Rapid prototyping therefore provides an important vehicle for incorporating quality and usability from the outset. Through realistic experience and interaction with the proposed user interface, users and user-interface designers can work together to detect and correct problems before a major development investment is made. The prototyping approach is especially powerful because it provides the opportunity for (1) early user feedback and performance data, (2) efficient, focused communication with users and developers, and (3) iterative design and test. In this paper we illustrate the prototyping and evaluating process with three examples of AT&T products and services.