Though much has been published concerning the intended or realized benefits of participating in a Problem-Based curriculum, we know little about what participants (faculty and students) actually do when they say they are doing Problem-Based Learning (PBL). The current paper is part of an ongoing to effort to apply methods borrowed from studies of discourse to understanding PBL as a form of enacted practice. In particular, the paper provides a description of the interaction within a PBL tutorial meeting leading to the generation of a Learning Issue (LI). We introduce the term Knowledge Assessment Segment (KAS) for important stretches of interaction during which participants identify learning issues. We present a detailed analysis of a selected segment. Specific features discussed include: how the group's perspective on a topic changes over the course of the discussion, the tutor's role in providing "scaffolding" for student reasoning, and the group's incorporation of "thinking about thinking." The purpose of descriptive studies of this sort is to enhance our understanding of what it means to do Problem-Based Learning.