Human population growth is and long has been the greatest threat to other species on the planet, to the ecosystems they and we depend on and to the attainment of a high standard of living for more people, now and in the future. More than a quarter century ago Garrett Hardin noted that the solution to this global problem was going to require, pragmatically, 180 different national population policies. Starting almost 20 years ago some ESA members, including an ESA president, began attempting to persuade ESA to deal with population issues more forthrightly in the white papers ESA occasionally puts together. The advice has been ignored. And when population issues have been raised within ESA, the preference has been, contra Hardin, to avoid discussion of U.S. overpopulation. This session hopefully will be a start to remedying that situation. Its focus is on U.S. population-environment issues, past, present and future. To provide a general framework for understanding such issues, the first presentations analyze U.S. population and economic trends and policies, and the possibilities and difficulties of estimating a ‘sustainable’ population for a country or of assessing environmental impacts of particular immigration policies. Later presentations focus on specific environmental problems related to population growth. Though our primary focus in this session is on the U.S., three of the problem areas selected for discussion are partly binational ones with Canada (oil sands operations, Pacific salmon) or Mexico (terrestrial wildlife in border regions). A fourth issue is exacerbation by the U.S. of one of the most severe global environmental problems (greenhouse gas levels in the atmosphere). Sociological and political phenomena in scientific and other subcultures that impede our progress are discussed in a final presentation.