The traditional medical curriculum and internships must be supplemented by standardized teaching modalities, such as computer-assisted instruction using patient simulators. A patient simulator is defined as a representation of a clinical situation in which an individual conducts the diagnosis and management of a patient. Advantages include allowing students to have access to conditions which may not be routinely encountered in the clinical setting, posing no risk to an actual patient, providing an enhanced sense of reality, providing immediate feedback, and evaluating a student's response. Development of the patient simulator in this study included an analysis stage to determine users' requirements and to model knowledge, the design stage to encode the models of knowledge, and the implementation stage to evaluate effectiveness. Twelve students from various academic fields evaluated the patient simulator for ease of use, consistency and speed, diagnosis and treatment scenario representation, accuracy of the clinical problem simulation, accuracy and value of the feedback and the effectiveness of the student evaluation models. The main conclusions were that the patient simulator is a useful tool in testing the diagnostic and treatment skills of medical students and that the user interface requires further development to ensure its full acceptance in the field of medical education. (Contains 16 references.) (AEF)