Despite the central role of boards in corporate governance, there has been relatively little understanding of their internal organization, specifically the structure of board committees. Using a dataset of over 6,000 firms, the authors find that committee activity, especially the number of committees, has been stable over time. Most of the familiar non-required board committees are rarely used. The majority of directors sit on multiple committees. The benefits and costs of a committee depend on its type. Overall, committees need to be more integrated into our understanding of corporate governance.