Most academic programmes that prepare students for the health professions have a long history of involving patients in teaching and learning. Until recently such involvement has been largely passive, but the last 20 years have seen major growth in the number and diversity of educational initiatives in which patients play an active role as educators. This article describes how and why these changes have occurred, identifies some of the challenges of learning from those outside the academy--and professions--and explores some of the questions raised about the nature of "professional" and "lay" knowledge and expertise.