This chapter explains how science is evaluated and used in decision-making for public policy measures and other actions that focus on reducing exposure to harmful environmental contaminants. It briefly reviews the current statutory approaches to regulations and policy decisions. The chapter explores what is lacking and needed for more effective and protective policy decisions. It presents some of the typical types of scientific information that are used to identify potential human health hazards from environmental chemicals. The chapter deals with some of the judgments/issues that arise when evaluating the information for use in the decision-making policy process. Most forms of public policies and decision-making require some toxicological knowledge for informing actions, though scientific information is only one part of the process, as decisions and policies are also influenced by politics, economics, and other external forces.