Next Generation Compliance is an EPA initiative to increase compliance with environmental regulations by using advances in pollutant monitoring and information technology combined with a focus on designing more effective regulations and permits to reduce pollution. Protecting clean air and water, and ensuring our communities are safe from pollution, is more complex today than ever. Whether it's pollution that's not apparent to the naked eye or large numbers of small sources that collectively have a big impact on the environment, new challenges require us to innovate and improve. Today's challenges require a modern approach to compliance with new tools and approaches while strengthening vigorous enforcement as the backbone of environmental protection. Next Generation Compliance principles have been used to build compliance drivers into rules, permits, and enforcement settlements, resulting in better environmental performance, while also enabling regulators to more easily monitor and ensure compliance. These principles are demonstrated by tools such as: -public accountability through increased transparency of compliance data, -electronic reporting, -advanced pollutant monitoring for point source discharges, -ambient monitoring in water bodies, both upstream and downstream from dischargers, and -third-party verification of compliance with environmental requirements. As authorized by the Clean Water Act (CWA), the National Pollutant Discharge Elimination System (NPDES) program controls water pollution by regulating point sources that discharge pollutants into waters of the United States. While Next Generation Compliance can and has been used across all environmental programs, this Compendium focuses primarily on use of Next Generation Compliance tools in the NPDES program to advance the goals of the CWA for point source discharges. These creative and innovative approaches illustrate how technological and behavioral advancements and efficiencies could improve compliance rates, increase transparency, and improve environmental performance.