Politics and science make strange bedfellows. In politics, perceptions are reality and facts are negotiable. The competing interests, conflicting objectives, and trade-offs of political negotiations often lend themselves to bending the truth and selectively interpreting facts to shape outcomes. In science, facts are reality. This collection examines the conflicts that arise when politics and science converge. In Politicizing Science: The Alchemy of Policymaking, eleven leading scientists describe the politicization-through misapplication or overemphasis of results that favor a political decision or through outright manipulation-of scientific findings and deliberations to advance policy agendas. They show how the consequences of politicization are inflicted on the public, including the diversion of money and research efforts from worthwhile scientific endeavors, the costs of unnecessary regulations, and the losses of useful products-while increased power and prestige flow to those who manipulate science. The authors of three essays describe government diversions of scientific research and the interpretation of scientific findings away from where the evidence leads and toward directions deemed politically desirable. Three more contributions analyze the expensive and extensive efforts devoted to altering images of risk in order to establish linkages in the public's mind between deleterious human health effects and various areas of scientific research. Two essays examine the workings and results of consensus advisory panels and conclude that their recommendations are often based on far-from-certain science and driven by social and political dynamics that substitute group cohesion in favor of independent, critical thinking. Authors of two essays describe the unfortunate results of application of the "precautionary principle," which generally requires proof of no risk before a new product is introduced or an existing product can be continued in use. A concluding essay describes the personal costs of opposing the politicization of science.