The report's major finding is that there is no overall, conceptually integrated Environmental Projection Agency (EPA) research program on extrapolation modeling, but a conglomeration of investigator-initiated projects, many of which are commendable in their design and implementation. The major recommendation is that EPA should develop a comprehensive plan for an extrapolation models research program that should: articulate an overall conceptual objective towards which individual projects would aim; enhance EPA's risk assessment-risk management philosophy; develop a framework that promotes more planning and resource stability in support of the research; provide a common nomenclature; improve communication among the Agency's organizational components; and explain to the nonscientist how the research on extrapolation models supports the Agency's regulatory decisions.