Problem-based learning in medical education: Developing a research agenda.

While the use of problem-based learning (PBL) methods continues to increase in medical education, three literature reviews of PBL have appeared in the past several years which come to different opinions about their merits. This analysis summarizes the research evidence regarding PBL by examining how well it has met its originators' goals, what we know about how PBL works, and how PBL fares in a goal-free comparison with conventional curricula. A research agenda is suggested to refine our understanding of well-documented effects of PBL, to probe for other possible longer term PBL outcomes, and to examine if and how PBL affects knowledge acquisition and retention. Consistency of evidence from a variety of PBL implementations can help decide whether the effects seen can be attributed to PBL or are the results of other curricular features unique to one setting.