Problems associated with telemedicine systems include high telecommunications costs, lack of physician interest, and failure to build evaluation into the design process from the onset of the telemedicine project. An overview of the human-factors engineering approach to systems design and how it can be applied to the development of telemedicine systems is described. Design of an interface is based on an analysis of user capabilities, tasks, and work environment. Task analyses are performed to understand and document the interaction between a user's work activities and a system. Two characteristics of a human factors approach that are important for telemedicine are: (1) defining and measuring user performance, and (2) involving users in the design and testing of a system. Usability goals are operationally defined and tracked to quantify performance. Having users participate in the design, testing, and critique of a system also increases the likelihood that the system will be accepted and used after it is released.