As a result of enforcement actions and settlements for noncompliance with federal pollution control requirements, the U.S. Environmental Protection Agency (EPA) reported that, for FY2011, regulated entities committed to invest an estimated $19.0 billion for judicially mandated pollution controls and cleanup, and for implementing mutually agreed upon (supplemental) environmentally beneficial projects. EPA estimates that these efforts achieved commitments to reduce, treat, or eliminate 1.8 billion pounds of pollutants in the environment, primarily from air and water. EPA also assessed more than $152.0 million in civil penalties (administrative and judicial) and $35.0 million in criminal fines and restitution during FY2011. Nevertheless, noncompliance with federal pollution control laws remains a continuing concern. The overall effectiveness of the enforcement organizational framework, the balance between state autonomy and federal oversight, and the adequacy of funding are long-standing congressional concerns. This report provides an overview of the statutory framework, key players, infrastructure, resources, tools, and operations associated with enforcement and compliance of the major pollution control laws and regulations administered by EPA. It also outlines the roles of federal (including regional offices) and state regulators, as well as the regulated community. Understanding the many facets of how all federal pollution control laws are enforced, and the responsible parties involved, can be challenging. Enforcement of the considerable body of these laws involves a complex framework and organizational setting. The array of enforcement/compliance tools employed to achieve and maintain compliance includes monitoring, investigation, administrative and judicial (civil and criminal) actions and penalties, and compliance assistance and incentive approaches. Most compliance violations are resolved administratively by the states and EPA. EPA concluded 1,735 final administrative penalty orders in FY2010. Civil judicial actions, which may be filed by states or EPA, are the next most frequent enforcement action. EPA may refer civil cases to the U.S. Department of Justice (DOJ), referring 222 civil cases in FY2011. The U.S. Attorney General's Office and DOJ's Environmental Crimes Section, or the state attorneys general, in coordination with EPA criminal investigators and general counsel, may prosecute criminal violations against individuals or entities who knowingly disregard environmental laws or are criminally negligent. Federal appropriations for environmental enforcement and compliance activities have remained relatively constant in recent fiscal years. Some contend that overall funding for enforcement activities has not kept pace with inflation or with the increasingly complex federal pollution control requirements. Congress appropriated $583.4 million for enforcement activities for FY2012, a decrease below the $593.5 million enacted for FY2011 and the $596.7 million enacted for FY2010, but an increase above the $568.9 million enacted for FY2009 and $553.5 million for FY2008. The President's FY2013 budget request included $615.9 million for EPA enforcement activities. To date, Congress has not completed action on the FY2013 appropriations for EPA.