This summary, issued by The National Academy of Sciences Board on Earth Sciences and Resources, examines how the U.S. Department of Housing and Urban Development (HUD) can use GIS to aid in the planning of affordable housing and urban decision making. Envisions HUD's joint role in the development of the National Spatial Data Infrastructure: advocating local needs and ensuring local data quality. Provides recommendations on improving data quality, extending the urban policy knowledge base, public outreach, and use of partnerships.