Thirteen epidemiologic studies of ingested asbestos conducted in five areas of the U.S. and Canada were reviewed and evaluated for the definitiveness and applicability regarding the development of ambient water quality standards. One or more studies found male or female associations between asbestos in water supplies and cancer mortality (or incidence) for neoplasms of the esophagus, stomach, small intestine, colon, rectum, gall bladder, pancreas, peritoneum, lung, pleura, prostate, kidney, brain, thyroid, and leukemia. Several methodological weaknesses and limitations were found in each study leading to the determination that no individual study nor aggregation of studies exists that would establish risk levels from ingested asbestos. A binomial probability analysis of the eight independent studies suggested that while the level of male-female agreement was generally low, the numbers of observed positive associations in males and females for neoplasms of the esophagus, stomach, pancreas, and prostate was unlikely to have been generated by chance factors alone, and thus, may have a biological basis related to ingested asbestos.