Authorities in 52 United States jurisdictions were contacted to determine the existence and structure of cancer reporting laws and registration systems. Of the 52 US reporting areas examined; 30 (58 per cent) had a law requiring cancer reporting; 36 (69 per cent) of the reporting areas had at least one centralized cancer registry covering a geographically defined population. Among the 30 areas with cancer reporting laws, 26 had population-based registries; of the 22 areas with no cancer reporting law, 10 had a population-based registry. Among the 30 areas with cancer reporting laws, 12 required one reporting source (hospital, physician, laboratory), 11 required two reporting sources, four required three reporting sources, two areas gave the health department the authority to designate reporting sources, and one did not specify any reporting source. While 11 of the laws provided legal protection for both the data provider and the cancer patient, eight did not specify any such legal protection. While 13 laws made provisions for research uses of cancer reporting data, 17 did not do so. None of the laws had ever been legally tested at or beyond the State Appellate Court level.