Purpose: The purpose of this study was to analyze the causes of the problems in Problem Based Learning (PBL) program performed in integrated curriculum of Hematology, Seoul National University College of Medicine, 2002, and to determine the improvement strategies for a successful PBL in integrated curriculum. Methods: This study was conducted using qualitative methods with participant observations, descriptive participants, in-depth interviews and an open questionnaire, etc. during the three days two weeks. Ten of 17 tutors including 10 faculty and 7 residents took part in the study. Among the 10 tutors, 7 were the faculty tutors, 3 were the residents tutors. The data was analyzed the causal chains which were developed by Colby. Results: The main problems revealed in implementing of PBL program were a large class size, lacks of tutors, time, budget, faculty education and college authorities interests in undergraduate medical education, etc. The main problem of a PBL program in an integrated curriculum of Hematology was the recruitment of tutors. According to the casual chains analysis, the factors that affected the recruitment of PBL tutors were related to college authorities lack of interest in undergraduate medical education. Conclusion: In order to have successful PBL program in an integrated curriculum, several administrative factors, including extrinsic reward systems such as promotion and tenure decision, and departmental budgetary requirements, should be considered.