C linical teachers differ from clinicians in a fundamental way. They must simultaneously foster high-quality patient care and assess the clinical skills and reasoning of learners in order to promote their progress toward independence in the clinical setting. 1 Clinical teachers must diagnose both the patient's clinical problem and the learner's ability and skill. To assess a learner's diagnostic reasoning strategies effectively, the teacher needs to consider how doctors learn to reason in the clinical environment. 2-4 Medical students in a classroom generally organize medical knowledge according to the structure of the curriculum. For example, if pathophysiology is taught according to organ systems, then the student's knowledge will be similarly organized, and the recall will be triggered by questions related to specific organ systems or other contextual clues. In the clinical setting, the patient's health and care are the focus. Clinical problems may involve many organ systems and may be embedded in the context of the patient's story and questions. Thus, in the clinical setting, the student's recall of basic science knowledge from the classroom is often slow, awkward, or absent. Only after learners make new connections between their knowledge and specific clinical encounters can they also make strong connections between clinical features and the knowledge stored in memory. 5,6 This report focuses on how clinical teachers can facilitate the learning process to help learners make the transition from being diagnostic novices to becoming expert clinicians. Di agnos tic R e a soning There is a rich ongoing debate about our understanding of the complex process of clinical diagnostic reasoning. 2,3 In this report, some of the basic processes involved in clinical reasoning, as understood according to current knowledge, are translated into practical and specific recommendations for promoting the development of strong diagnostic reasoning skills in learners. The recommendations are illustrated by a clinical case presentation. Clinical teachers observe learners gathering information from patients, medical records, imaging studies, results of laboratory tests, and other health care providers. On the basis of their observations, and through the discussion of clinical cases, teachers draw conclusions about the learners' performance, including their reasoning processes. A hypothetical case provides an example of a conversation involving a patient, two learners with different levels of expertise, and the clinical teacher (see Box). In this case, 7-9 a patient with knee pain makes an urgent visit to an ambulatory care practice. A novice resident (with relatively little experience with this patient's problem, which is gout) and an expert resident (who is familiar with this problem, having seen other patients with gout) each independently interviews the patient, performs