Problem-based learning outcomes: ten years of experience at the University of Missouri-Columbia School of Medicine.

PURPOSE: To add to a previous publication from the University of Missouri-Columbia School of Medicine (UMCSOM) on students' improvement in United States Medical Licensing Examination (USMLE) Step 1 and Step 2 scores after the implementation of a problem-based learning (PBL) curriculum by studying the performance of ten PBL class cohorts at the UMCSOM. METHOD: Characteristics of graduating classes matriculating in both traditional and PBL curricula, 1993-2006, were compared for Medical College Admission Test component scores, undergraduate grade point averages, performance on the USMLE Step 1 and Step 2 exams, faculty contact hours, and residency directors' evaluations of UMCSOM graduates' performance in the first year of residency. RESULTS: Mean scores of six of the ten comparisons for USMLE Step 1 and six of nine comparisons for USMLE Step 2 are significantly higher (p < .01) for UMCSOM PBL students than for first-time examinees nationally. These differences cannot be accounted for by preselection of academically advantaged students, increased time on task, or reduced class size. Gains in performance continue into residency, as evidenced by program directors' perceptions of superior performance of UMCSOM PBL graduates. CONCLUSIONS: The PBL curricular changes implemented with the graduating class of 1997 resulted in higher performances on USMLEs and improved evaluations from residency program directors. These changes better prepare graduates with knowledge and skills needed to practice within a complex health care system. Outcomes reported here support the investment of financial and human resources in our PBL curriculum.