The Agency for Toxic Substances and Disease Registry (ATSDR) protects the health of human populations that live near hazardous waste sites in the United States. Since 1990, ATSDR has used GIS to evaluate the demographic characteristics of populations around sites; identify features in the community that are relevant to the protection of populations; monitor health-related data and health complaints by community members; and overlay contaminant distribution with census data to characterize subpopulations that may be potentially susceptible to site contaminants due to their age, sex, race, or socioeconomic condition. Release data can also be modeled and displayed in a GIS to estimate exposure potential to site contaminants. Through the use of GIS, ATSDR is able to develop a unified database of site-related information that can be used from the initial site characterization through communication of health-related information to the public. GIS provides a common relational environment for the integration of disparate data sets. Through ODBC and RDBMS connectivity, health assessors are able to keep abreast of the most up-to-date site-related data both locally and through the Internet. The future of public health is bright. Data integration through GIS and mapping provides tools for enhanced health protection.