The Science Advisory Board's Radiation Advisory Committee was requested to review the scientific merit of a proposal to conduct an epidemiological study of radon in indoor air. The Board accepted the request and formed a Radioepidemiology Subcommittee which responded to two overriding scientific issues: Can further epidemiological study contribute to an understanding of the risks of lung cancer associated with household exposures. The Subcommittee concludes that scientific uncertainties in current epidemiological studies (chiefly studies of uranium miners) could be further reduced through direct investigations of the domestic population. Is the proposed study under review by the Office of Research and Development, entitled Health Effects of Waterborne Radon, appropriately designed to address the risk. For reasons cited in the attached report, the Subcommittee concludes that it is not appropriately designed.