Recent and forecasted advances in microbiology, molecular biology, and analytical chemistry have made it timely to reassess the current paradigm of relying predominantly or exclusively on traditional bacterial indicators for all types of waterborne pathogens.? Nonetheless, indicator approaches will still be required for the foreseeable future because it is not practical or feasible to monitor for the complete spectrum of microorganisms that may occur in water, and many known pathogens are difficult to detect directly and reliably in water samples.?This comprehensive report recommends the development and use of a "tool box" approach by the U.S Environmental Protection Agency and others for assessing microbial water quality in which available indicator organisms (and/or pathogens in some cases) and detection method(s) are matched to the requirements of a particular application.? The report further recommends the use of a phased, three-level monitoring framework to support the selection of indicators and indicator approaches.?Table of ContentsFront MatterExecutive Summary1 Introduction and Historical Background2 Health Effects Assessment3 Ecology and Evolution of Waterborne Pathogens and IndicatorOrganisms4 Attributes and Application of Indicators5 New Biological Measurement Opportunities6 A Phased Approach to Monitoring Microbial Water QualityAppendix A: Emerging and Reemerging Waterborne PathogensAppendix B: Review of Previous ReportsAppendix C: Detection TechnologiesAppendix D: National Research Council Board Membership and StaffAppendix E: Committee Biographical Information