AGNESS is an expert system shell developed at the University of Minnesota. AGNESS is more general than other shells. It uses a computation network to represent expert defined rules, and can handle any well-defined inference method. The system works with non-numeric as well as numeric data, and shares constructs whenever possible to achieve increased storage efficiency. AGNESS uses a menu-driven user interface, and has several features that make the system friendly and convenient to use. The system includes eight explanation queries designed to increase the amount of information available to the user, the expert, and the knowledge engineer while remaining simple enough to be included in most of today’s expert system shells. AGNESS has been tested on several domains ranging from simplified problems to real world medical analysis.