This document describes a strategy for conducting wildlife effects research within the U.S. Environmental Protection Agency's (EPA) National Health and Environmental Effects Research Laboratory (NHEERL). The Strategy is designed to address critical research areas and produce methods, models, and findings that the EPA Program and Regional Offices, the States, and Tribes can use to conduct wildlife population risk assessments and to develop associated criteria. Consistent with the EPA's ecological risk assessment guidelines, the Strategy is designed to improve problem formulation, effect characterization, and risk characterization steps. Within this context, the Strategy supports a tiered approach to wildlife risk assessment and criteria development by arraying a series of assessments from most general and broadly based (screening level) to most realistic, accurate, and situation-specific (definitive level). While the sustainability of wildlife populations remains the assessment endpoint of concern throughout the tiered approach, increasingly accurate and realistic models and data are needed in higher tier risk assessments to narrow the band of uncertainty around the estimate of risk. The Strategy proposes development of a suite of methods and models with increasing realism and accuracy that will first concentrate on lower-tier risk assessment and criteria needs then on research that provides techniques and approaches for higher-tier applications. Specifically, the Strategy is focused on three major research objectives: 1. Develop mechanistically based approaches for extrapolating toxicological data across wildlife species, media, and individual-level response endpoints. 2. Develop approaches for predicting population-level responses to stressors. Identify the responses at the individual level that have the greatest influence on populationlevel responses. 3. Develop approaches for evaluating the relative risks from chemical and nonchemical stressors on spatially structured wildlife populations across large areas or regions. The proposed research across these three objectives will provide increasingly sophisticated methods and models for avian, amphibian, and mammalian wildlife risk assessments and criteria development.