<div>This volume collects recent studies conducted within the area of medical education that investigate two of the critical components of problem-based curricula--the group meeting and self-directed learning--and demonstrates that understanding these complex phenomena is critical to the operation of this innovative curriculum. It is the editors' contention that it is these components of problem-based learning that connect the initiating "problem" with the process of effective "learning." Revealing how this occurs is the task taken on by researchers contributing to this volume. The studies include use of self-reports, interviews, observations, verbal protocols, and micro-analysis to find ways into the psychological processes and sociological contexts that constitute the world of problem-based learning.</div>