The U.S. Clean Water Act calls for the minimization of "adverse environmental impact" at cooling water intake structures. To facilitate an exchange of information among all stakeholders in the issue, the Electric Power Research Institute organised a national symposium in 2001 to discuss the meaning of adverse environmental impact and methods for its assessment. Technical experts in federal and state resource agencies, academia, industry and non-governmental organizations attended the symposium. This is a collection of peer-reviewed papers, intended both to inform and to encourage the development of rules regarding the minimization of adverse environmental impact at cooling water intake structures.