Abstract This is a study of illegal dumping using a randomized control group (RCT) design with two experimental arms. Researchers have documented that deteriorated vacant lots are strongly associated with crime and violence, including firearm violence, and that greening vacant lots by mowing them or enhancing their appearance with landscaping can help to restore social capital, improve sense of safety, and reduce crime and violence. Yet, resident-engaged greening efforts (shown to enhance greening effects for violence prevention) are often undermined by illegal dumping, defined as the repeated disposal of waste though improper, often clandestine methods. Vacant lots experiencing illegal dumping are at even higher risk for violence and crime, due to the increased physical disorder on these sites. Cities with elevated vacancy and economic disinvestment across the U.S. devote significant time and resources to remediating dumping activity. Despite the severe and widespread nature of illegal dumping, few researchers have systematically studied this issue or identified viable modes of prevention. The purpose of this randomized control trial is to evaluate the effects of a community-developed illegal dumping prevention intervention on county owned vacant lots with repeated reports of illegal dumping in Flint, MI, a city with concentrated vacancy and economic disadvantage, on violent crime. We will examine the effects of two different approaches (dumping intervention plus resident-engaged maintenance vs. dumping intervention) onto illegal dumping prevention on physical disorder and violent crime, including firearm related police incidents, relative to control sites receiving no intervention. We will further examine the effectiveness of the intervention with and without community engagement, in which neighborhood residents maintain and monitor the dumping prevention intervention. To study the sustainability of each of these two approaches, we will test the effects of a subset of the dumping prevention sites longitudinally. We will also study displacement of dumping by tracking overall dumping reports across the city and examining if new dumping sites are appearing near the remediated sites. Finally, we will conduct cost effectiveness and cost-benefit analyses of the intervention with and without resident engaged maintenance for both costs of dumping removal and violent and firearm-related crime averted. We will work in partnership with the Genesee County Land Bank and Center for Community Progress to implement the study and disseminate study results, cost-benefits, and best practices for implementation through their community and national networks.