In this article, the authors describe an active learning exercise which has been used to replace some lecture hours in the renal portion of an integrated, organ system-based curriculum for first-year medical students. The exercise takes place in a large auditorium with ~150 students. The authors, who are faculty members, lead the discussions, which are based on two clinical cases developed from actual patient data. The cases have already been published in the American Physiology Society Teaching Archive ("objects 195" and "3814"). The PowerPoint slides used in conjunction with the exercise were produced with Turning Point software so as to take advantage of clicker questions, which have been shown to facilitate active learning. (Contains 5 figures.)