Abstract
ILIAD is an expert system written in C for the Macintosh computer. The system operates in two modes: as an expert consultant to teach differential diagnosis and as a knowledge-based patient case simulator to teach and test medical problem solving. This paper describes ILIAD's simulation mode. Since relations between a disease and its manifestations are expressed in probabilistic terms within ILIAD's knowledge base, a wide variety of simulated cases can be generated automatically. The student's performance may then be evaluated by comparing his or her problem solving approach to an “optimal” strategy derived from the ILIAD knowledge base. This tool is especially valuable in providing experience with diseases that students otherwise are unlikely to see during their medical training.