The performance of pharmacists in using an interactive computer-based patient simulation program and their attitudes toward the simulations are reported. The Institutional Patient Medication Simulation program is designed to enhance and evaluate the medication problem-solving skills of pharmacists. Each simulation consists of patient data-gathering, case question, and therapy decision modules with initial assessment and monitoring nodes. Five simulations were tested: gout, urinary-tract infection, congestive heart failure, antimicrobial prophylaxis in surgery, and hypertension. Pharmacists from nine hospitals were recruited for the study. Participants were asked to perform the simulations within a specified period and to complete attitudinal questionnaires. Of the 91 pharmacists who volunteered, 72 (79%) completed the simulations and the questionnaires. The practitioners indicated that the simulations adequately tested their knowledge and that they would recommend them to colleagues. Performance scores for data gathering were less than 70%, with no significant differences among the simulations. Case question scores exceeded 80% and again were consistent among simulations, whereas therapy decision scores were more variable, with the lowest scores being recorded for antimicrobial-related simulations. Pharmacists with more hospital experience tended to perform better. Pharmacists completing a patient simulation program found the simulations to be worthwhile. Performance scores indicated some difficulty in gathering patient data and showed that correct therapeutic decisions may not always occur even if adequate information is obtained.