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Beginning with a set of books and articles published in the 1950s, cognitive psychologists have developed a new descriptive theory of how people make decisions under conditions of risk and uncertainty. A dominant theme in the theory is that most people do not evaluate risky circumstances in the manner assumed by conventional decision theory-they do not, that is, seek to maximize the expected value of some function when selecting among actions with uncertain outcomes. The purpose of this article is to consider some implications of the cognitive theory for regulatory policies designed to control risks to life, health, and the environment. Section I describes the theory and outlines the key differences between it and conventional decision theory. Sections II and III then address, in turn, two central questions about the uses of the theory. First, if people behave in the manner described by the cognitive psychologists, how will this shape the demands that citizens make, through the political system, for risk regulation, and how (if at all) might these demands differ from those that would be expected if citizens behaved, instead, in the manner assumed by conventional decision theorists? Second, if citizens make demands as predicted by the cognitive theory, how (if at all) might their behavior affect the regulatory responses that political actors supply?