As part of the research leading to the implementation of computer-based case simulations (CCS) for the licensing examinations of the National Board of Medical Examiners, gender differences in performance were studied for one form consisting of 18 cases. A secondary purpose of the study was to note differences in style or approach that might differentiate the performance of men and women at a more detailed level than overall rating. In CCS, the examinee is presented with an introduction to the patient's signs and symptoms and then enters patient management plans into the computer. The simulated patient's condition changes in response to the action requested by the examinee. The sample in this study was 201 senior medical students. Gender identification was available for 118 men and 78 women. Performance on the total set of cases was similar for men and women, with the average of case means 4.55 for men and 4.51 for women. The two cases with the largest performance difference favoring women were obstetrics-gynecology cases, and an emergency surgery case had the largest difference favoring men. At the item level, results suggest that men tend to request more beneficial and inappropriate actions than women, although the effect was small. Overall, the performance differences on the CCS cases were very small, as expected. (Contains 6 tables and 10 references.) (SLD)