This paper presents a randomized field experiment on community-based monitoring of public primary health care providers in Uganda. Through two rounds of village meetings, localized nongovernmental organizations encouraged communities to be more involved with the state of health service provision and strengthened their capacity to hold their local health providers to account for performance. A year after the intervention, treatment communities are more involved in monitoring the provider, and the health workers appear to exert higher effort to serve the community. We document large increases in utilization and improved health outcomes-reduced child mortality and increased child weight-that compare favorably to some of the more successful community-based intervention trials reported in the medical literature. (c) 2009 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology..