Although many recent studies have discussed specific issues related to problem-based learning in medical education, a comprehensive review of the literature on the consequences of its use and the outcomes of curriculum based on problem-based learning have not been accurately looked at. Furthermore, there is no available review that critically evaluates challenges and barriers to the implementation of problem-based learning curriculum in medical schools. The purpose of this part is to highlight the major challenges and barriers reported during curriculum preparation and implementation and to critically evaluate the consequences of problem-based learning introduction and its educational outcomes.