An assessment of the effects on human health of reclaimed water. The assessment compares health data on cancer incidence, mortality, and cases of infectious disease in the Montebello Forebay area, which has received some reclaimed water in its water supply for almost 30 years, with a control area that received no reclaimed water. The epidemiologic study took an ecologic approach, in which the unit of analysis is a group of people, not an individual. The results of the study do not provide evidence that reclaimed water has an adverse effect on health.