'State-Society Synergy for Accountability' is part of the World Bank Working Paper series. These papers are published to communicate the results of the Bank's ongoing research and to stimulate public discussion. The central question guiding this study is: How can the relationship between the state and society be transformed from a process of particularistic demands into a healthier engagement that produces policy outcomes serving the public interest? The paper first surveys the literature on accountability and establishes a categorization of the different ways by which civil society can interact with the state. It then explores in detail seven case studies of successful experiences of state-society synergy for accountability. The studies are drawn from a wide range of different contexts - Brazil, India, Mexico, the United States - and from a variety of areas of government activity including corruption control, environmental regulation, poverty reduction, election monitoring, infrastructure provision, school reform, and police reform. The paper concludes with a series of lessons for development practitioners on how best to initiate, design, and implement successful accountability mechanisms grounded in state-society synergy.