Abstract. Of critical importance is the design of the man-machine interfaces for general rule based systems. They must serve (i) as user-friendly interfaces for different classes of users for different applications and (ii) to invoke service components in integrated packages without interrogating users. These objectives are achieved with a multitier interface design whose two parts, the Interactive User-Friendly Interface (IUFI) and the System Interface (SI), communicate with each other via commonly used notational systems and can be invoked independently of each other. The user-friendly interface, which is uniquely designed for each user discipline, passes information to the SI. The SI does not change for new IUFI designs and it can be invoked by other rule based systems without interrogating users.Here the requirements for the IUFI and SI parts are identified, four different designs of multi-tier interfaces are given and two applications are described. Also included are guidelines for designing user friendly interfaces,