These Agency-wide guidelines are provided to improve the quality and consistency of EPA's ecological risk assessments. As a next step in a continuing process of ecological risk guidance development, the guidelines draw from a wide range of source documents including peer-reviewed issue papers and case studies previously developed by EPA's Risk Assessment Forum. The Guidelines expand on and replace the 1992 report Framework for Ecological Risk Assessment. A major theme of the guidelines is the interaction among risk assessors, risk managers, and interested parties at the beginning (planning and problem formulation) and end (risk characterization) of the risk assessment process. In problem formulation, the guidelines emphasize the complementary role of each in determining the scope and boundaries of the assessment, selecting ecological entities that will be the focus of the assessment, and ensuring that the product of the assessment will support environmental decision making. The risk characterizaton section discusses estimating, interpreting, and reporting risks and applies an ecological perspective to recent Agency policy encouraging clear, transparent, reasonable, and consistent risk characterizations. The Guidelines' emphasize that the interface between risk assessors, risk managers, and interested parties is critical for ensuring that the results of the assessment can be used to support a management decision. The Guidelines are internal guidance for EPA and inform the public and the regulated community regarding the Agency's approach to ecological risk assessment.