Lack of validity and reliability in selection procedure for internship at teaching hospitals has become a nationwide serious issue, especially regarding its influence on undergraduate medical education. This article describes a case model of selection procedure for internship at Seoul National University Hospital aiming for appropriate measurement of clinical competency as well as a meaningful feedback to the undergraduate medical education. The modification of selection was based on two parts; a problem-based written examination and a clinical skill-attitude assessment. For the former, a total of 60 test items for 34 problem cases were developed, being provided with a variety of pictorials and figures to simulate a real clinical setting. The knowledge level of all test items were either interpretation or problem-solving, and multi-answer items were randomly included to minimize a risk of high chance scoring in multiple choice items. The clinical skill was assessed with 10 important skills with predesigned check list. We conclude that problem-oriented written examination together with clinical skill assessment is a way of improving the measurement of clinical competency and strengthens clinical clerkship effectively during the undergraduate clinincal studies.