Fact. Cancer is a relatively common yet greatly feared disease. Belief. The concept that cancer is largely preventable is widely held by advocate groups, the press, and Congress. Belief. The concept that carcinogens at any level of exposure pose a significant cancer risk to human is widely believed by the public. Fact. In contrast to this belief, carcinogens are now known to be widespread in the environment and that virtually all substances are contaminated with carcinogens at some albiet low level. Fact. The solution to the ubiguitous presence of carcinogens cannot be solved by regulatory fiat. Fact. Often the only viable solution to regulating carcinogens is setting maximum levels of acceptable exposure (tolerances). Belief. In U.S. society, the process of establishing tolerances must be conducted in the open, providing adequate opportunity for public comment. Fact. The courts will sustain regulatory agency decisions about risks only if the administrative procedures used comply with the Administrative Procedures Act and if the technical methodology used is in good standing. Fact. For the method to be in good standing it cannot be a recent invention created after the fact to solve the issue at hand but must instead be a procedure that is claimed to be generally applicable to determining or estimating cancer risk. Belief. QRA should be an orderly procedure or process by which cancer risk estimations are conducted in an unbiased manner. As such it is fundamentally acceptable to the courts for resolving disputes. Fact. However, because QRA is dependent upon a large number of assumptions and because regulatory agencies feel compelled to act in a conservative, risk-adverse manner, risk estimates are often criticized for being over stated. Belief. To make risk estimates more realistic, data or facts must substitute for worst case assumptions. Fact. This process of substituting scientific facts for assumptions is occurring but it is expensive, time consuming, and not always possible. Nevertheless, it constitutes a major opportunity for improving the process by which risk estimates are made.