This paper considers conceptual, analytic and policy issues concerning US population, immigration and environment. The policy question guiding the analysis is whether the environmental impact of immigration is proportional to its numbers, i.e., additions to the population, or does immigration have a disproportionate effect on the environment, i.e., above or below what would be expected on additional numbers alone? If the effect is proportional, then policy issues concerning the environmental impact of immigration become centered on population policy and programs, and the relative benefit of manipulating immigration as a component of population growth to achieve national environmental (or other) goals. If, however, immigration has a disproportionate effect, thus an effect on the environment beyond the contribution to population growth, then US immigration policy and its administration have unique environmental implications which may be appropriately addressed through immigration policy reform. The IPAT model is presented as a general framework for establishing the proportionality of the environmental effects of US immigration. Given the demands of theory and limitations of data, the framework is decidedly’ ideal‘and is offered as a long range proposal for policy relevant research on US population, immigration and environment. In order to move to act on the proposed research agenda, however, several important analytic components of national population and environmental research must be strengthened. First, more accurate and comprehensive measurement of the components of US population growth is critical. Second, analysis of population, immigration and environmental processes must occur over time and across regions and local communities in the US. Third, a process of interpreting research results which is both inter- and multi-disciplinary, and is inclusive of national, regional and local concerns must be organized to wisely interpret findings within the context of national goals and traditions.