The Comprehensive Epidemiologic Data Resource (CEDR) is the Department of Energy's (DOE) electronic database comprised of health studies of DOE contract workers and environmental studies of areas surrounding DOE facilities. DOE recognizes the benefits of data sharing and supports the public's right to know about worker and community health risks. CEDR provides independent researchers and the public with access to de-identified data collected since the Department's early production years. Current CEDR holdings include more than 80 studies of over 1 million workers at 31 DOE sites. Access to these data is at no cost to the user. Most of CEDR's holdings are derived from epidemiologic studies of DOE workers at many large nuclear weapons plants, such as Hanford, Los Alamos, the Oak Ridge reservation, Savannah River Site, and Rocky Flats. These studies primarily use death certificate information to identify excess deaths and patterns of disease among workers to determine what factors contribute to the risk of developing cancer and other illnesses. In addition, many of these studies have radiation exposure measurements on individual workers. CEDR is supported by the Oak Ridge Institute for Science and Education (ORISE) in Oak Ridge, Tennessee. Now a mature system in routine operational use, CEDR's modern internet-based systems respond to thousands of requests to its web server daily. With about 1,500 Internet sites pointing to CEDR's web site, CEDR is a national user facility, with a large audience for data that are not available elsewhere.