This report presents a research plan for an assessment of risks to biodiversity. The plan describes the theoretical basis of the research approach and the data and methods to be used in the assessment. Initial research activities are formulated as a set of pilot studies that will examine nine research questions concerning the assumptions, data, and methods of the approach. A collection of government, academic, and nongovernmental organizations, called the Biodiversity Research Consortium, has developed this research approach and prepared the plan. Authors of the plan represent current members of the Consortium.