The Waterborne Disease and Outbreak Surveillance System (WBDOSS) collects data on waterborne disease and outbreaks associated with recreational water, drinking water, and environmental and undetermined exposures to water. WBDOSS is a national surveillance system that was initiated in 1971 as a partnership between the CDC, the Council of State and Territorial Epidemiologists (CSTE), and the U.S. Environmental Protection Agency (EPA). This system is dependent on public health departments in individual states, territories, and the Freely Associated States (composed of the Republic of the Marshall Islands, the Federated States of Micronesia and the Republic of Palau; formerly parts of the U.S.-administered Trust Territories of the Pacific Islands) to provide complete and accurate data for waterborne disease and outbreaks. Although initially designed to collect data about drinking water outbreaks in the United States, WBDOSS now captures outbreaks associated with recreational water, drinking water and other non-recreational water exposures. Annual or biennial surveillance reports of the data collected by the WBDOSS have been published in CDC reports from 1971 to 1984 and in the Morbidity and Mortality Weekly Report (MMWR) from 1985 to the present. Data from WBDOSS have supported EPA efforts to develop drinking water regulations and have provided guidance for CDC’s recreational water activities, such as the Healthy Swimming program. Waterborne disease and outbreak reporting to the WBDOSS transitioned from a paper-based system to the electronic National Outbreak Reporting System (NORS) in 2009.