A Disciplinary Commons involves a group of 10-20 educators from diverse institutions who teach the same course meeting monthly during an academic year. The participants prepare a detailed portfolio describing their own teaching of the course in monthly increments, critique each other's portfolios, and visit each other's classrooms. This combination of critical self-examination and peer review helps them understand their own teaching, identify places where innovation and change are needed, share what works, borrow from others, and see their own teaching in the context of a broad range of possibilities.