The power to inform is one of GIS's strongest features. Health professionals, including epidemiologists, environmental health scientists, and medical geographers have long made the connection between geography and population health. The etiology and spread of disease, the exposure to toxic chemicals, the accessibility to health care, the discovery of medicines, the response to health emergencies such as natural and man-made disasters, all benefit from the extensive use of GIS technology. GIS is the way population health data stored in the health records of births, deaths, hospital admissions, physician office visits, clinical trial outcomes, immunizations, tumors, and injuries are linked to environmental data such as toxic air, water, land, and infrastructure data relevant to health care such as roads, locations of medical facilities, and population demographics. Medical researchers are also discovering the inherent power of GIS to improve the quality and value of medical imaging data where spatial proximity of organic anomalies is a critical factor in medical diagnosis and treatment. As the demand for better health and more accessible health care grows more intense, the need for GIS in every health organization will also grow—from local and national health authorities to the professional health care associations whose mission is to improve the practices and science of their members. For more information about GIS in health and human services, visit www.esri.com/health on the Web.