Surveillance of outbreaks of waterborne disease is jointly conducted by the Center for Disease Control (CDC), Atlanta, Ga., and the Environmental Protection Agency (EPA), Cincinnati, Ohio. Waterborne outbreaks are reported to the CDC and EPA by state and local health departments and by water supply agencies, and the data are tabulated annually. In 1978 more cases of waterborne disease were reported than in any year since surveillance was initiated in 1971, and for the first time, two agents, Campylobacter fetus subspecies jejuni and a Norwalk-like virus, were well documented as causes of waterborne disease outbreaks. This report summarizes reported outbreaks of disease related to drinking water that occurred in the United States in 1978.