• Carrying Capacity Network
• Center for Environment and Population
• Comprehensive U.S. Sustainable Population (CUSP)
• The Population Environment Connection (EPA Report)
• Malthus' Original Essay on the Principle of Population
• The Population Council
• Population Action International
• Population Coalition
• Population Index
• The Population Institute
• Population Reference Bureau
• Population Environment Balance
• Scientists for Population Reduction
• Sierrans for US Population Stabilization
• SprawlCity
• Union of Concerned Scientists
• United Nations Population Information Network
• US Census Bureau
• World Overpopulation Awareness
• World Population Film/Video Festival

Regional Organizations

• Californians for Population Stabilization
• Floridians for a Sustainable Population
• New Hampshire Citizens for Sustainable Population
• Vermont Earth Institute
  
• Minnesotans For Sustainability
  
  

• The Center for Immigration Studies
• Federation for American Immigration Reform
• U.S. Immigration and Customs Enforcement
• Migration Dialogue
• Numbers USA
• The Social Contract
• United to Secure America
• US Border Control
• US Commission on Immigration Reform
  
  

• Audubon Society
• E Magazine
• Friends of the Earth -- US
• Leadership for Environment and Development (LEAD) -- Ecological Footprint Calculator
• League of Conservation Voters Environmental Scorecard
• Natural Resources Defense Council
• Sierra Club
• The Wilderness Society
• WorldWatch Institute
• Zero Waste America