BACKGROUND:Systematic trends in examinee performance across the testing day (sequence effects) could indicate that artifacts of the testing situation have an impact on scores. This research investigated the presence of sequence effects for United States Medical Licensing Exam (USMLE) Step 2 clinical skills (CS) examination components. METHOD:Data from Step 2 CS examinees were analyzed using analysis of covariance and hierarchical linear modeling procedures. RESULTS:Sequence was significant for three of the components; communication and interpersonal skills, data gathering, and documentation. A significant gender x sequence interaction was found for two components. CONCLUSIONS:The presence of sequence effects suggests that scores on early cases are influenced by factors that are unrelated to the proficiencies of interest. More research is needed to fully understand these effects.