The purpose of this study was to assess third-year medical students' competency for development or revision of the undergraduate curriculum and assessments. One hundred and twenty-seven third-year medical students at the Pusan National University were included in the study. After third- and fourth-year students took a common written examination, clinical performance examination (CPX), and objective structured clinical examination (OSCE) with common items as a summative assessment, the third-year students' competency was compared with 132 forth-year students' results. The correlation of the written examination and CPX/OSCE was analysed, and the summative results were compared with the grade point average (GPA) through the second year, CPX/ OSCE in the second year, and GPA in the clerkship. On the written examination, the third-year students' mean score was lower than the fourth-year students' by over 11 points, whereas the gap in the CPX/OSCE was 4 points and there was no difference in the OSCE. There was a moderate correlation between the written examination and the CPX/OSCE scores (R=0.371, p<0.01). The written examination was highly correlated with GPA through the second year, which mainly evaluated medical knowledge (R=0.771, p<0.01). A relatively high correlation was observed between CPX/OSCE scores and GPA in the clerkship (R=0.641, p<0.01). The summative CPX/ OSCE scores showed a moderate correlation with formative CPX/OSCE scores in the second year (R=0.464, p< 0.01). The third-year students' score was quite low on the written examination and slightly low on the CPX/OSCE compared to that of the fourth-year students. The written examination and CPX/OSCE cannot replace each other and should be combined with other methods of evaluation to measure competency. Early OSCE and workplacebased assessment should be useful in the early assessment of clinical skills competency.