SURFACE is a prototype expert system built for the personal computer to assist in the selection of surface analysis techniques for characterizing the surface of minerals or other materials. SURFACE uses a production system to represent the expertise required to reach a decision. The system knowledge base runs on an inference engine (shell) developed by A. M. Starfield and S. K. Adams (1984). SURFACE was built in a two-stage process consisting of (1) development of a rule base for surface analysis from information in the literature and (2) testing and refining the rule base by several means, including interviews with human experts.