ABSTRACT
Objective To evaluate the impact of different rating instruments used by raters with different seniority in OSCEs. Methods Surgical interns were randomly divided into two groups to undertake a nine－station surgical OSCEs. Raters with different seniority were also divided into two groups with four senior raters and four junior raters in one group. OSCE results were compared. Results There was no statistical significance when comparing results from different raters using checklist rating instrument. Results from different raters using global rating scale instrument were significantly different. Correlations between raters using checklist and global rating scale instruments showed statistical significance in 81.3% of stations. Conclusion Checklist rating instrument showed high capability of repeating the results. Therefore, it is recommended to apply checklist as many as possible in OSCE exams with mixed rater seniorities. Research on design of rating instruments are to be investigated to insure the effectiveness as well as the credibility of the rating system.