These guidelines are provided to improve the quality and consistency of Environmental Protection Agency`s ecological risk assessments. The guidelines draw from a wide range of source documents including peer-reviewed issue papers and case studies previously developed by the Agency´s Risk Assessment Forum. A major theme of the guidelines is the interaction among risk assessors, risk managers, and interested parties at the beginning and end of the risk assessment process. In problem formulation, the guidelines emphasize the complementary roles 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 characterization 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.