Abstract This paper describes human-computer interaction issues within the development of an engineering design support system using a case study. The study takes a design support system for externally pressurized journal bearings as an exemplar. The issues presented focus on aspects of the system interface design and design interaction aids. The design principles of a system user interface are formulated from functional, aesthetic and structural perspectives. The principles are concerned with using metaphors, implementing direct manipulation, consistency design and aesthetic integrity, which are described in detail through the design of system interface elements such as icons, pull-down menus, screen layout and sound usage. The interaction aids for a designer using the system is discussed with particular reference to a knowledge-based system approach. The aids include the initial determination of values of design parameters, the monitoring of the computed parameter values and the final evaluation of the design outputs. With these aids, a designer can intuitively overview the design process and learn to control the process interactively. Human-computer interaction issues are important in establishing user satisfaction with system specifications such as the system interface, user-friendliness, performance speed and learning time.