Public concern about the health effects of low-level ionizing radiation exposure has increased in recent years. Therefore, GAO undertook a study to determine what definite conclusions, if any, can be drawn from current scientific knowledge about the cancer risks of low-level ionizing radiation exposure and what conclusions can be drawn about the best direction for current and future federal research. The immediate goal of the federal research program is to develop a database for estimating the risk of low-level radiation exposure. The long-term goal is to understand the mechanisms and processes of how radiation causes cancer. Data from two studies involving low-level radiation were analyzed; a literature search was conducted; and the current status of ionizing radiation research was reviewed. As yet, there is no way to determine precisely the cancer risks of low-level ionizing radiation exposure, and it is unlikely that this question will be resolved soon. There is a continuing need for federally sponsored research in this area, and GAO believes that federal research efforts can be strengthened. It also agrees with the objectives of current congressional and executive branch initiatives to coordinate federal research efforts in this area. The Interagency Radiation Research Committee, recently formed by Presidential memorandum, is such an important area that GAO believes a federal interagency research review group should be created by legislation. Epidemiologists have used estimates of the number of cancers induced by high-level exposures to radiation to predict the numbers that may be induced by lower exposures. These predictions can vary widely depending on which of several mathematical equations is used. An intensive effort to synthesize the results of radiation research might be accomplished by developing quantitative theories of radiation carcinogenesis and critically testing their predictions with cellular and animal experiments.