Corruption and mismanagement of public resources can affect the quality of government services and undermine growth. Can citizens in poor communities be empowered to demand better-quality public investments? This paper looks at whether providing social accountability training and information on project performance can lead to improvements in local development projects. It finds that offering communities a combination of training and information on project quality leads to significant improvements in household welfare. However, providing either social accountability training or project quality information by itself has no welfare effect. These results are concentrated in areas that are reported by local officials as more corrupt or mismanaged. The impacts appear to come from community members increasing their monitoring of local projects, making more complaints to local and central officials, and cooperating more. The paper also finds modest improvements in people's trust in the central government. The study is unique in its size and integration in a national program. The results suggest that government-led, large-scale social accountability programs can strengthen communities' ability to improve service delivery.