Geographic information systems (GIS) and digital computer technology will advance the mission of the Centers for Disease Control and Prevention (CDC) and Agency for Toxic Substances and Disease Registry (ATSDR) to protect public health. Geographic positioning, topology, and planar and surface measurements are basic GIS properties which enable highly precise locational referencing of spatial phenomena. The growing uses of remotely sensed imagery and satellite facilitated global positioning systems are contributing to unprecedented surveillance of the environment and greater understanding of known and suspected environmental disease associations with human and animal health. Earth science and public health monitoring GIS databases offer new analytic opportunities for disease assessment and prevention.