How can nonprofit organizations and NGOs demonstrate accountability to stakeholders and show that they are using funds appropriately and delivering on their promises? Many nonprofit stakeholders, including funders and regulators, have few opportunities to observe nonprofit internal management and policies. Such information deficits make it difficult for 'principals' to differentiate credible nonprofits from less credible ones. This volume examines a key instrument employed by nonprofits to respond to these challenges: voluntary accountability clubs. These clubs are voluntary, rule-based governance systems created and sponsored by nongovernmental actors. By participating in accountability clubs, nonprofits agree to abide by certain rules regarding internal governance in order to send a signal of quality to key principals. Nonprofit voluntary programs are relatively new but are spreading rapidly across the globe. This book investigates how the emergence, design, and success of such initiatives vary across a range of sectors and institutional contexts in the United States, the Netherlands, Africa, and Central Europe.