People who want to tackle tough social problems and achieve beneficial community outcomes are beginning to understand that multiple sectors of a democratic society-business, nonprofits and philanthropies, the media, the community, and government - must collaborate to deal effectively and humanely with the challenges. This article focuses on cross-sector collaboration that is required to remedy complex public problems. Based on an extensive review of the literature on collaboration, the article presents a propositional inventory organized around the initial conditions affecting collaboration formation, process, structural and governance components, constraints and contingencies, outcomes, and accountability issues. that have merged into a new entity to handle problems through merged authority and capabilities. In the midrange are organizations that share information, undertake coordinated initiatives, or develop shared-power arrangements such as collaborations (which may be a distinct organizational form) in order to pool their capabilities to address the problem or challenge. We thus define cross-sector collaboration as the linking or sharing of information, resources, activities, and capabilities by organizations in two or more sectors to achieve jointly an outcome that could not be achieved by organizations in one sector separately.