The aim of ergonomics in design is to maximise the human contribution to system performance, and to ensure that users are not overloaded in their activities. The optimum ‘allocation of functions’ between the users and the rest of the system must be achieved, and the user-system interfce must be compatible with human capabilities and limitations. Task descriptions, and approaches to modelling user behaviour, help in this. Both the hardware interface and the software interface are important in computer-based systems. Other aspects of system design with substantial ergonomics content are procedural aids, the workspace and environmental aspects. Good ergonomics practice demands comprehensive consideration of all the facets of human interaction with the system.