The mission of the United States Environmental Protection Agency (EPA) is to protect human health and safeguard the natural environment. EPA was established to implement and enforce environmental regulations passed by the U.S. Congress to control pollutants discharged into the air, water, and land. To implement these regulations, EPA develops test procedures (analytical methods) to measure regulated pollutants. These methods are contained in regulations codified at Title 40 of the U.S.Code of Federal Regulations(40 CFR). Nearly all of the current test procedures are prescriptive, meaning that they contain exacting procedures for performing tests. Recently, EPA has initiated an effort to implement a performance-based measurement system (PBMS) that will introduce flexibility in conducting environmental monitoring. This initiative will encourage analytical innovation by allowing the use of new and alternate methods provided that predetermined performance criteria are met. This article presents an overview of EPA's analytical methods programs and implementation of PBMS and provides detailed information on EPA's wastewater monitoring program.