Purpose: We conducted objective structured clinical examinations (OSCEs) in medical students both before entering clinical clerkship and after finishing clinical clerkship for the purpose of evaluating the usefulness of OSCEs before clinical clerkship. Methods: The subjects of the study comprised 77 3rd-year medical students who participated in a 2-week course of physical diagnosis before clinical clerkship, and 98 4th-year medical students who had completed their clinical clerkship. The OSCE consisted of 17 cases and 17 stations for the 3rd-year medical students, and 20 cases and 28 stations for the 4th-year students. We assigned 4 minutes and 30 seconds to each station. OSCE stations were duplicated at two sites and were performed twice. After the OSCE, we used structured questionnaires to survey the subjects for their opinions of the current process and the need for an OSCE. Results: At the psychiatric station, which applied an identical scenario and checklists to both the 3rdand 4th-year medical students, the mean score of the 3rd-year medical students was significantly lower than that of the 4th-year students. The correlation coefficient between OSCE score and cumulative performance grade of 3rd-year medical students (r=0.29) also was lower than that of 4th-year medical students (r=0.53). Over 80% of the 3rd-year medical students and over 90% of the 4th-year responded that an OSCE is necessary. However, around 70% of students preferred an OSCE for each clinical class during clinical clerkship, and only 33～38% of students preferred an OSCE as a final examination. Almost all students wanted to receive feedback after an OSCE. Conclusions: Performing an OSCE on 3rd-year medical students before they enter clinical clerkship provides better preparation for the clinical clerkship than an evaluation alone. We suggest that an OSCE should be used as a formative assessment in addition to a summative evaluation such as a final examination.