- PURPOSE: To further examine the objective structured clinical examination (OSCE) as a performance-based assessment method for clinical ethics. METHOD: In the spring of 1993, a volunteer sample of 88 final-year medical students from all five Ontario medical schools took a four-station OSCE that used standardized patients and involved decisions to forego life-sustaining treatment. Performance was scored on a checklist of behaviors unique to each case. Data were analyzed for reliability using intraclass correlation coefficients and the Spearman-Brown prophecy formula. RESULTS: Reliability of the test was only .28 as a result of a low average inter-station correlation of .07. To achieve a test reliability of .8, 41 stations (almost seven hours of testing time) would be required. CONCLUSION: Because of its low test reliability, the OSCE is not a feasible stand-alone method for summative evaluation of clinical ethics. This performance-based evaluation method should be combined with other, more reliable evaluation methods. The OSCE has promise for formative evaluation.