To monitor the possible effects of radiation on Americans who were in Japan during the 2011 earthquake, tsunami and subsequent damaged Fukushima Daiichi nuclear power plant, the U.S. Army Public Health Command has launched the Operation Tomodachi Registry website. The site provides location-based radiation dose estimates for the approximately 70,000 department-affiliated adults and children who were in one of 13 mainland Japan locations at the time of the disaster, which included the release of radiation into the environment. It will serve as a public clearinghouse for information on the U.S. Defense Department's response to the crisis in which U.S. troops assisted their Japanese counterparts in relief efforts. The Operation Tomodachi website will be used to build a model for future exposure registries that could be used to manage a range of other events or activities where the potential for environmental exposure to harmful chemical or biological agents is possible. It will be managed as part of the Defense Occupational and Environmental Health Readiness System. Names, locations and radiation exposure information for service members, civilian contractors, employees and their family members is contained in a secure database.