This research project was initiated to facilitate the use of waterborne asbestos data for a possible case-control epidemiological study of ingested asbestos in five Bay Area counties near San Francisco, California. For each county, and each census tract within the area, information about historical water supply and distribution, water treatment practices, and asbestos levels has been compiled. It was determined that none of the major water districts servicing the San Francisco Bay Area are free of asbestos fibers. Individual asbestos measurements range in value from less than 10,000 fibers per liter to 1.8 x 10 to the 8th power fibers/liter of finished water. It was determined that a sampling protocol to augment the current asbestos data base should include sampling the largest flows of water and should take into consideration: variation within the distribution system, possible seasonal variation, the drought of 1976-1978, and the historical waterborne asbestos levels.