This talk will cover theoretical and empirical work on cooperation in organizations. Using the literature on repeated games and relational contracts as a starting point, we will discuss how firms, communities, associations, and other organizations can build and maintain cooperative relationships among their members. We will complement this discussion with results drawn from the small but rapidly-growing empirical literature on cooperative relationships. Throughout, the talk will emphasize the challenges that must be overcome and the trade-offs that must be made in order to build and sustain productive relational contracts.