Even as attention to our nation's lake resources has sharpened in the past decade, water quality surveys repeatedly indicate deteriorating lake water quality. Several recent surveys indicate that the percentage of lake and reservoir waters impaired or threatened by pollution is higher than that of streams, rivers, estuaries, or groundwaters. This paper was prepared to stimulate debate on the need for specific numerical standards for managing water quality in lakes and reservoirs, and argues for them. A panel of reviewers representing different interest groups debated the issues presented in this paper at a plenary session at the 1986 Conference of the North American Lake Management Society; comments from the debate and additional opinions follow the paper. The principal authors also worked with contributors from a wide variety of institutions in writing this paper. This brought viewpoints ranging from engineering and agricultural perspectives in the university community to local, state, and federal government organizations. After reviewing the status of water quality in U.S. lakes and reservoirs and discussing innovative, comprehensive approaches for achieving point and nonpoint source pollution reduction, the authors conclude that degradation of our lake resources is a very serious national problem, one that does not appear to be adequately addressed by existing institutions. The paper addresses alternative lake protections approaches – from technology-based point and nonpoint control standards, to lake inflow or in-lake water quality standards and innovative watershed-based practices – the advantages and limitations of using simulation modeling to establish standards, and the importance of biological monitoring in establishing ecologically-based standards. Case studies illustrate the utility and limits of the various approaches. The paper particularly emphasizes a case study of watershed-based, point/nonpoint pollution reduction tradeoffs in Colorado, and a watershed-based, special classification system and non-point source control cost-sharing program for eutrophic reservoirs in North Carolina. The authors suggest possible federal and state approaches for using specific, numerical or ecologically-based standards to restore and protect lake and reservoir water quality.